Genie TACH signal (Short Crank) Module Bench Test!

[@roberthogue6797]

Ivan, I have to say I really admire your willingness to not only admit you may have been wrong, but to show how you check to see if you were. Bravo!!

[@PineHollowAutoDiagnostics]

These are the best opportunities to learn :)

[@roberthogue6797]

Pine Hollow Auto Diagnostics It’s funny you’d say that, I think all your videos are the best opportunity to learn! You’d be surprised at the number of KZbinrs that not only wouldn’t admit if they made a mistake but that would get pissed over something as simple as simply suggesting how to verify IF they had screwed up.

[@davidkegler7886]

Pine Hollow Auto Diagnostics . Subscribed. Very transparent diagnosis and good reflection.

[@ryanjohnson4239]

As a professional MEWP Technician I really appreciate your going the extra length to tear into how the module works. One thing I have seen over the years on the genies, especially the kubota powered ones, is that tach signal wire comes out of the alternator behind an aluminum cover. I've seen lots of those rub through due to vibration, not sure what yours looked like on there but something to look out for on future service calls. I enjoy your channel and all the fun diagnostic toys you pull out to play with.

[@PineHollowAutoDiagnostics]

Thanks for the comment, Ryan! It's exciting to learn more about these lifts. I enjoy variety in my daily work :)

[@ryanjohnson4239]

I've been working on them almost exclusively for 25 years. Hit me up if you need some information that you can't find on your own.

[@malkeetvirdi3582]

interesting. I have a genie z45-25 that wont start even when the ism has been replaced.

[@fluffyblue4006]

Great analysis. I've been watching quite a lot of automotive diagnostic vids already, from you, Eric, Keith, and others. Thought I've seen it all. But this in-depth analysis of this Genie starting issue keeps your channel very interesting. Thanks. I can't get enough of these kind of analysis vids.

[@PineHollowAutoDiagnostics]

Thank you for the feedback! I always like to bench test components to really learn the good vs bad behaviors 🙂

[@HandyC]

@DiagnoseDan definitely a favourite

[@rp5029]

You totally geeked out on us Ivan...I love it! lol

[@BigDaddy_MRI]

Two things: tach signal conditioning. The original module SC circuit has fatigued and isn’t doing its job. Leaky capacitor, etc has already been mentioned. Second: If this module has a microcontroller, then there should be an ignore tach command in the firmware that causes the controller to ignore the tach signal for “x” amount of milliseconds. This way the tach signal can stabilize and give valid information. The new module has newer firmware that has changed or lengthened the ignore tach signal for a bit longer and makes it more reliable. Companies do this all the time. There may have been a recall of the original module for just this reason. I’d check on that. Or a combination of both. I’d start with checking all the electrolytic caps on the board.

[@PineHollowAutoDiagnostics]

Great tips, Harry. That makes sense!

[@Graham_Wideman]

Ivan: I noted from the last video that the module contains 40106 Hex Schmitt inverters (ie: with hysteresis inputs) that are almost certainly used for cleaning up the input signals. Your measurement of 0.9V hysteresis requirement corresponds to typical hysteresis of 40106 input when powered from 5V. The 40106 may well be running on 5V -- there are a couple of components in the module that could be a 5V regulator to power the 40106 and the PIC MCU. Or the 40106 could be running on a higher voltage, and the input tach signal might feed through a resistive voltage divider before going to the 40106. It seems likely that there would be some passive circuitry between the module input terminals and the 40106, including clipping diodes to prevent a voltage arriving at the 40106 that is outside the 40106's power/ground rails by more than 0.6V or so.

[@PineHollowAutoDiagnostics]

This is awesome, in-depth info on the circuits, Graham! Thank you for the insight!

[@willemstreutgers1154]

Ivan i have great respect for the way you work. I had the same with a Volvo 245 from '88 only 298.000 miles (just run in) on the clock same sort of intermittent probs. It is a Calif. car so lots of electronics (Chrysler ignition) to keep the enviorment clean. Just disconnect every contact and clean it then petroleum gelly on it. After done all of that it runs perfectly. We are going up to the 1.000.000 miles with that car.

[@CubasAutomotive]

Awesome followup! I like to see the thought process. It's hard to do all the testing needed on site, as time is of the essence and we can feel it. That fact that the new module had no issues also reassures the call you made, so that in itself makes it a tough call to continue more scope testing. The honesty in the conversation is why I enjoy hearing even more. I mean, you can only do so much sometimes....

[@PineHollowAutoDiagnostics]

Thanks for the comment Cuba! Yeah it's always tough to remember to get all the data that you need on a construction site. Sometimes it's hard to think with all the noise around! But that makes it more exciting as well :)

[@marscruz]

Had a similar Function Generator at work back in the 90's and an analog Tektronics 2 channel scope. Good troubleshooting technique. You found all the pertinent parameters and rolled into and out of them at their limits. If you get called out again for that customer (you know you will eventually) then maybe you will remember to look at the Tach signal again. Thanks for the followup and demonstration. Cheers Ivan.

[@carltonlane8931]

A few years ago ,i had some carrier fridges and auto start,now here’s the thing,unit 1 say did the genie thing,swapped out auto start module all ok,unit 2 failed fit the old first module ,all ok,this video has brought back all my conversations from years ago,we had come to the conclusion the tac signals wear noisy,great video thanks.just reminiscing,thinking.

[@Charles_Mulberry_7977]

You are as smart as a tach! Ivan, you would make a excellent tech school instructor.

[@Graham_Wideman]

Smart-as-tack tech tests tach!

[@PineHollowAutoDiagnostics]

I Iove a good pun Carlos 😁

[@tinkerwest]

Firstly, I don't understand how someone commented about your being wrong as it was indeed a faulty start module. What did I miss?🤔 Secondly, its about damn time you purchase a part for a repairs! 😁 Lastly, I'd love to have seen some bonus footage of the module's autopsy. 😷

[@tommiller4490]

It's been many years since I used my electronics brain and Hitachi oscilloscope I would have had a hard time following without your great breakdown.Thanks for the refresher in troubleshooting!

[@SmittySmithsonite]

Wouldn't it be nice if manufacturers put this information out there? Imagine that! I won't be holding my breath for that one ... Great analysis, Ivan! 👍🍻

[@wagoosh78]

we are always learning its a applied science and that is what makes it FUN !

[@Nudnik1]

Some modules get moisture in them. Put them in a refrigerator for a week sucks water out of circut board chips etc. A vacuum chamber also evaps water. Also sometimes metal chips get on rpm pickup sensors causing weak signal. Had a CAT JLG found that issue. Excellent work Thanks

[@Graham_Wideman]

There is no rpm pickup sensor in this case. The tach signal comes from a tap on the output windings of the alternator.

[@Nudnik1]

@@Graham_Wideman ok a gas motor. I found that issue on a CAT Perkins diesel JLG dealership could not fix . Sensor was full of metal chips from flywheel teeth caused computer and electronic speed control to lock up. On my channel

[@PineHollowAutoDiagnostics]

Interesting note on the metal chips! I have a case study coming up on a JLG with a Kubota engine with similar symptoms :)

[@wyattoneable]

You dove in real deep on this one. It is interesting to see how you come up with the data.

[@billk5727]

Very interesting case study Ivan! Learned a lot here! Thanks again! TakeCare, Bill

[@DaveSender66]

Ivan I admire your persistence. Nice work!!!!!

[@ADVANCEDLEVELAUTO]

Nice setup! I need to get myself one of them function generators.

[@PineHollowAutoDiagnostics]

Yeah they have some pretty kick ass affordable modern ones on Amazon. This one I got from the salvage pile, and it's not too reliable lol

[@engeneer_ru5827]

The most likely, it seems to me, is a software upgrade in the PIC. It is interesting to look at the circuitry of the new control module.

[@robertmccully2792]

The quest for knowledge makes good video.

[@mikechiodetti6737]

I worked in electronics for a while, came back to automotives. I wish so many times that I had my old power supply and frequency generator. Diagnosing out of the box to locate the source of the problem. I've done that in the past with my DMM and old 2 channel Fluke scope. Seems ancient now compared to the Pico, but it worked! Hopefully that Genie will be the only one that gives you problems.

[@R.E.HILL_]

You really do not wanna be a parts changer, do you..? Lol!😂 Cool video, looking forward to the next one.. ☺

[@thebaldmechanichardatheari1124]

I think you have different filters in the second module which is probably making a better signal from the tach.

[@jannepo]

Or the input capacitor in the original controller has gone bad. When you feed a 16V square wave to capacitor all day long that is a tough job for the cap. That is why they use low ESR caps in the switching power supplies and should have used here too. Ivan, can you open the unit and check the input stage? Maybe there is a cap you can change and have an operational unit again?

[@AP9311]

Woooohooooi!!! Some serious bench testing! Now we will find out what the heck is going on! I have not watched it yet. Will post my comments after the video :)

[@unencumbered]

Wish I had time to have that fun...or you're making time for us:) Well done Ivan!

[@BABA-ws5eo]

Great video. Even if you replaced a module that is still good, I would not call it a "Pine Hallow Parts Canon". From a practical standpoint, you can only do so much on the job site in the mud. You also didn't talk about cost of the module. If your labor time would cost more than the module, then that's something else to consider too. That's great how you are double checking to see if the part is good or not after the repair. Most people would just toss it out, and never learn as much as you are.

[@joshclark6101]

You continue to impress. Amazing

[@bundylovess]

You hit the nail right on the head with the filtering Ivan big thumbs up

[@woodstar109]

Boom I learn so much from your channel, understand a lot but not all but I'm trying

[@baxrok2.]

Still a lot of what if's, however if it's running reliably then you fixed it. Thanks!

[@sufferinsilence6474]

Need to test the new module and see if the thresholds are the same so you know definitively.

[@Paul1958R]

Ivan, Thank you for that great video and analysis! This type of video is what I love - real analysis of the data to find the root cause of an issue. Im learning so much from you. God bless Paul (in MA)

[@PineHollowAutoDiagnostics]

Thanks for the feedback, Paul!

[@rmr5740]

Too late Ivan, you are now the "Pine Hollow Parts Cannon" . . . jk.

[@bobparrott8130]

👍 I totally agree, crank signal is poorly pulsing... kinda looks like interference of some kind or maybe just a week sensor ? Interesting, please us informed... thanks

[@Graham_Wideman]

The tach signal comes from the alternator stator winding center point, not a sensor per se.

[@gregorykellerman3876]

I believe standard TTL considers anything below 1.5 volts a logic low and anything at or above 3.5 volts as a logic high. In between is more or less a no mans land.

[@Graham_Wideman]

Ivan: The 6.3V lower limit on the module operation is probably the dropout voltage for the one or two voltage regulators on the module that probably provide 5V for the MCU and 40106.

[@vincescalise4821]

Another great teaching video thank you Ivan for taking the time

[@valentingeorgiev5001]

Great analysys. The 6.3V lock up voltage is probably a power watchdog chip - when the voltage goes below threshold the watchdog holds the RESET ping of the CPU active to prevent the CPU from doing stupid things. When the voltage goes up, the WD releases the reset pin, the CPU's program starts from the beginning and reacts to the inputs. Someone mentioned in the original video that the big electrolytic capacitors of the module might be on the way out. That would explain power fluctuations during startup. The capacitors cannot filter good enough the voltage and it drops too low. Have you inspected the capacitors with a magnifying glass? A little bulging at the cap or the sides is a clear sign. Or there could be bulging at the bottom of the cap which is harder to spot. Bad capacitors could also affect the reading of input signals since the input circuit is also affected by the bad power supply voltage. Another possibility is the new controller to have a updated firmware with fixes for such erratic crank signal at startup. I really enjoy your channel. I'm also an electronic engineer and like fiddling and repairing things including cars when I can and have the time. Growing up in Eastern Europe my dad and I were constantly repairing the family Жигули - stripping the entire car bare bone to replace the rusted out floor, rotted structural elements, etc. Engine rebuild, clutches, brakes, you name it. Those cars are dead traps but run forever (it still runs being made in 1975) with lots of repairs and welding :-)

[@doctorjohn-burgtekie]

Thanks Ivan reminds me of tech training.

[@bostedtap8399]

Great transfer from on site to bench test simulation. I assume the engine rpm feedback is for remote starting, and starter motor protection. Excellent Professor Ivan. Thanks for sharing.

[@billziegmond4943]

I am geeking out. I love all the science and testing.

[@garyhardman8369]

Ivan. Electronic engineer, In addition to Automotive engineer.

[@davidmelbourne5480]

Good analysis. Frequency derivation for the start determination is probably done in the microcontroller (in this case PIC) firmware. You did not show us the new non-oem one, maybe they improved it? It is likely that the new one has either an improved algorithm (maybe faster uP) or input smoothing components. Could still be an off-value cap in the signal conditioning part of the original - you may have guessed right after all. Could also be that noisy tach startup signal that the original module reacted badly to - I was trying to think of a way to feed the recorded the signal to the original module again to reproduce the problem. Great work Ivan, interesting video.

[@billrimmer5596]

So the rpm signal is like a crank signal. I wonder what the air gap is and if there r a bunch of metal particles in it potentially causing a problem. It isn't a vrf signal. It seems to be a Hall Effect. Nobody probably scopes those signals. Even the factory techs probably follow a flow chart. They also have a bunch of stock of parts to substitute until they get the right one. Great series. "I Dream of Genie"

[@for2utube]

Great video. Reminds me of a time I was troubleshooting why my '83 BMW R100RT was dying intermittently at a red light. Eventually traced it to a bad hall-effect sensor. Would get baked in heat, fail for about 90 seconds, then work again. I didn't own a scope back then. Wonder if you have an unusual gap, causing a choppy/noisy signal at low rpm.

[@bobweiss8682]

Too bad you cant compare the time delay between tach signal meeting threshold and the start relay dropping out, between the old and new modules. THAT is where the problem likely is. A shorter delay on the old module would likely be caused by an electrolytic capacitor in a timer, one-shot, or integrator circuit that has increased leakage or lost capacitance, both typical failure modes.

[@JD-iu3vi]

How do we know it has a time delay circuit? It may just be looking for a specific threshold to be met. The starter is going to turn the engine only so fast. The tach signal has to get above that frequency to be considered as an engine running condition. If the tach signal is noisy then it could fool the sense circuit. The newer circuit components could have different values or tolerances are better so it could be looking for a slightly higher tach frequency or level. Who knows without a schematic and circuit specs. But also like you say if it is time delayed then if electrolytics are part of the timing circuit they may have started to dry up from age changing their value. We can only guess without all the details.

[@Graham_Wideman]

Almost certainly the tach input voltage goes through a minimal network of resistors and diodes (maybe a cap) to clip it 5V, then into the 40106 schmitt-input inverters for hysteresis, then into the PIC microcontroller, likely an interrupt input, which would be responsible for measuring the pulse frequency and thus RPMs. So the input signal voltage threshold would be set by the 40106 input characteristics (they have 0.9V hysteresis when powered by 5V, matching Ivan's observations), possibly modified by input resistor arrangement. The RPM (frequency) threshold would be set by the PIC MCU programming. The MCU would also implement any other criteria like "must be over X RPM for Y seconds".

[@Graham_Wideman]

@Sam S If you're asking whether I could design this module and build it, yes. This one is pretty simple. Though we are somewhat guessing the precise details that this one actually implements, of course!

[@Graham_Wideman]

@Sam S I'm not sure your interests in this, but these books might appeal: www.amazon.com/Car-Hackers-Handbook-Penetration-Tester/dp/1593277032, www.amazon.com/J1939-Programming-Vehicle-Simulation-Arduino/dp/1938581180

[@andrewthompsonuk1]

Circuits that do this sort of thing may sound simple however there is many things that can go wrong.

[@Tracks777]

lovely stuff

[@Tracks777]

lovely video

[@roadkill5333]

Wow! Nice job! Definitely left me wondering how I make it through everyday life, without help! What's that old saying? "IF I WERE ONLY AS SMART AS IVAN "! Lol I must keep at it, as I hear education will soon be free, and I will need the smarts, to build a raft to escape to Cuba!

[@86753091974]

If it continues to cause a problem you could wire in a relay over the top of it. One side of the relay control could be from the cranking input. The other relay input could be wired to the charging system bulb warning indicator) it will most likely be ground when key is on (because alternator is not charging). This would eliminate someone cranking engine if the engine is already started. That's because if the engine is running the charging system warning bulb will be out (or a power not a ground) this would not allow the started to crank. Hope this makes sense. (Btw I suspect that is the whole purpose of that cranking circuit....they dont want it cranking accidentally if the engine is running)

[@thomasbyzewski2687]

I like your make it work for now attitude When your in the field. Construction worker are there to do their job. If You tell them to ring the bell and jump Up and down 3 times and it will start They will do it to get the job done.

[@russellstephan6844]

Nice deep dive! Bravo!

[@richardcranium5839]

love this video ivan spot on !!! looking at that waveform the noise in that signal is definitely of concern however i'm wondering if that is a function of the sensor and its wiring or is it an artifact caused within the old module. typical chicken or egg thing.

[@chadhelmer3835]

It would be interesting to see if the amount of load on the relay outputs would change any of the test data. Such as, a relay coil that is drawing excessive current from the module....is there potential of that variable that you don't have in the test, having an impact on the outcome?

[@PineHollowAutoDiagnostics]

good question. Relay itself was fine, and the test light simulates a comparable load, so I think the module driver has enough power to not kill itself :)

[@tiredoldmechanic1791]

Do you know for certain that it is using the signal from the alternator for an rpm reference? If so, it could be a fault in the alternator causing the trash in the signal. I guess that it makes sense as that lift can have a gasoline/propane or diesel engine. Both would have an alternator but only the gasoline/propane engine would have an ignition system. It seems that the primary reason for having that system is to prevent the starter being activated while the engine is running and shutting down the starter on engine start would be more of a secondary consideration. It can be difficult to tell if the engine is running from the basket at a distance. There would be times when it is necessary to crank the engine for an extended period if it ran out of fuel or in cold weather but normal cranking speeds seldom reach 300 rpm.

[@fieldsofomagh]

Caps losing value over time and in extreme temperature variations,outdoors could effect the normal operation of the module. The fact that a new module corrected the problem suggests that the original components on the pcb board had deteriorated sufficiently enough for the Genie to malfunction. Perhaps an individual component assessment might unearth the affected part.

[@kimvansteenkiste5665]

The starter looks quite new, what if a wrong type of starter is mounted, causing a to high cranking rpm? Normally that would not be a direct problem. However the cranking rpm you measured/calculated seems quite high and close to an engines idling rpm. It could cause the module shutting down the start relay, because it thinks it is already idling, while in fact it has just started turning, and to short, to have a reliable start.

[@PineHollowAutoDiagnostics]

Cranking rpm is about 300rpm, low speed once it starts is about 1,600rpm. Module turns off start relay once engine is over 800rpm.

[@dwoodog]

I'd still like to see some of the individual components in the module tested like the capacitors or transistors.

[@BobPegram]

Me too! How do out of spec capacitors affect the received signal? Usually electrolytic caps fail by losing capacitance and becoming more resistive. I think most of the controller is fine, e.g. transistors, or it wouldn't work at all. Perhaps the tachometer has slight problems as well.

[@BobPegram]

If I had been a better EE student, I could probably answer my own questions. 8-(

[@stephendee7839]

Did you try to run a dc supply to the tach signal input? I wonder if the module looks at the rms voltage rather than frequency. Would be an easier strategy and would mean the module wouldn't care about signal noise. If that was the case and there was a voltage spike when the starter moved, then that might explain why it shut off the instant the starter started turning.

[@PineHollowAutoDiagnostics]

If your rms voltage theory is correct, then the module would have shut off the start relay when i had the DC offset dialed up :)

[@zx8401ztv]

I wonder if there is a taco pulse capacitor/resistor filter in that unit thats a bit low on capacitance. That might filter less the high frequency out of the taco signal. Having the voltage and frequency changing the starting, sounds a bit naff. So a relay cutting the tach wire while cranking is a no no then :-D

[@PineHollowAutoDiagnostics]

A relay cutting the tach signal... Why didn't I think of that?

[@zx8401ztv]

It's not the russian way ha ha :-D

[@fluffyblue4006]

I noticed you stacked a bunch of cassette tapes in front of a speaker. I'd move those cassettes away from that speaker and away from anything containing permanent magnets. If you leave those cassettes for long enough or close enough to a magnet, you will notice intermittent drop-outs, starting with the highs. Intermittent, because half of the spool is closer to the magnet than the other half. Quite interesting effect but very annoying to listen to music on that way.

[@PineHollowAutoDiagnostics]

Lol all of those tapes are 20 to 30 years old and have been looped hundreds of times! I even had to tape a couple back together... Still sound decent 😁

[@andrewthompsonuk1]

I wonder if the tac. sensor is not the one the designer of the controller specified?

[@peterjohnston8116]

Great presentation ! Thanks.

[@heyitsdrew]

so what you clean up the tach signal and you're good. how do you do that? add ground? add a capacitor? an INDUCTOR? Some EMI filter?

[@randyhughes5160]

Ivan what about temperatures and moisture like a old ford distributor relay when it would get hot it failed cool off and run cracked soldier or it was muddy out there dampness changes the value

[@hpelisr]

Maybe starter overload? could have effected the module, from jumping in cold weather, accidental surge from touching the jumper's? may have starter problems.

[@mattmanyam]

It has a new starter (previous video)

[@hpelisr]

@@mattmanyam Ok, the old starter could have affected the circuit board?

[@hpelisr]

@@mattmanyam Some manufactures have a caution warning about jump starting, and how to do.

[@uchefred6300]

Good evening from here Mr pine, please am an Automobile Electirican am having a problem with Genie z-60/34.the machine is not driving fast,is very slow. What can I do please help me. Thanks for your understanding. I love what you'r doing brother keep it up.

[@randy1ization]

what if the starting battery isnt sending enough amperage to satisfy the tach before the module times out?> seems like a very critical timetable.

[@kthwkr]

3.1V and 2.2V sounds like typical logic input level min and max voltages required to trigger a high or a low. Above 3.1V and it's a high. Below 2.2V and it's a low. And that sounds like 5V cmos logic. Where the 5V cmos spec is 1.67V and 3.3V and if you measure you find it's just a little higher and lower respectively because they built in some headroom. But my guess is a cap has gone bad. It's always an electrolytic cap. Replace all the electrolytics. I have fixed many pieces of oddly functioning gear by replacing the electrolytics. Just fixed an old audio limiter by replacing the electrolytics. Re-capped my Fender Twin and the hum has gone away. Fixed many computer LCD monitors where the electrolytics for the backlight power supply had gone bad. And lot's of general audio and digital gear I've fixed just by replacing the electrolytics without bothering to actually track down the problem. The best situation for an electrolytic is a room temp environment and voltage always ON. If you have an audio amplifier or any stereo gear or VCR or anything like that. Leave it plugged in and ON all the time. I have audio power amps I have left on and unused for 10 years. They still work just fine. The only fear is a lightning strike. I have a small pile of equipment that I have on a timer that cycles the power on everyday for 30 min. TV sets too. If you put it away unpowered for 5 years it will likely not be working when you pull it back out. The electrolytic plates will collapse and start touching and the unit is shot until you replace the electrolytics. I have a VCR that has exactly that problem right now. Next time I need to play a VCR tape I will have to replace the electrolytics in the player first. That day may never come though. I bet that genie sat out in the hot sun and got hot enough in the summer to degrade the electrolytics. Pop open that module and replace them all. Especially check for areas inside the unit where a component is generating heat. If there is an electrolytic near it then it is likely to have gone bad. Electrolytics go bad in heat. Look on the PCB for any burned or browned area as a clue to hot components. How close is that module to engine heat? Any electrolytics near that area need to be replaced but better to replace them all. Electrolytics in 100C will go bad in just a few weeks. You don't have to use exact replacements. A higher voltage rating is fine. Generally a slightly higher capacitance rating by 50% and even 100% is OK. And get the best temperature ratings that are reasonably priced. Digikey should have what you need. If you read the datasheet for most electrolytics for their time to fail at higher temperatures you will be shocked to find that many can only survive weeks at temperatures that just don't seem that hot. Also, in the burned or browned areas check the carbon composition resistors. Prolonged heat will also change their value. The carbon composition resistors are usually the ones that drift with heat. They will look charred. It was common for designers to use carbon comp resistors when they needed a 1W or higher rating. Newer designs stay away from carbon comp. But I would bet your module was designed years perhaps decades ago and they just keep using that design even on brand new models because the cost of re-designing and re-proving that module prohibits a change. Most of the semiconductors, if they are working at all then they have survived the heat just fine. The semi's generally don't degrade by much or at all. And they can take much higher heat than electrolytics and carbon comp resistors.

[@enricopolazzo33]

7 volts seems a bit low during start up. Was the battery replaced?

[@simclardy1]

Excellent video

[@tedohio3038]

Great video. Can you explain the rpm unit that sends the single to the module ?

[@Graham_Wideman]

In this case, it's the tach output from the alternator. The alternator has a stator (stationary) winding that has three phases. Loosely speaking, three coils joined in a star shape. All else being equal, as the the alternator rotor turns, each coil generates a sine(ish) voltage, with the three outputs being 120 degrees apart from each other. The center connection point of the coil also follows a wave form waveform. Actually, the three coil output wave forms are made quite square by virtue of diodes that take the coil outputs and apply them to charging the battery (or running the equipment). That in turn affects the shape of the center-connection waveform. At any rate, that center connection signal is the alternator tach output, that is used as input to the starter module. Its frequency is proportional to alternator rotation frequency and hence also to engine RPM (since the engine drives the alternator by belt and pulleys of some fixed ratio.)

[@PineHollowAutoDiagnostics]

@@Graham_Wideman I definitely learned something new here... So the signal is not specifically conditioned by the alternator cicuitry to look nice and pretty?

[@Graham_Wideman]

@@PineHollowAutoDiagnostics Well if the alternator tach output (actually labelled "stator" on the Genie schematic) is simply the center connection on the stator "Y" coils, then there's no special prettification. I don't have personal experience with these, so I don't know what's customary. Sometimes schematics that show internals of some assembly are "suggestive" rather than actual. But the waveform you captured looks reasonable for just a raw connection to the stator midpoint. (well, except for the "dropout" glitch that you spotted!). Basically a sine waveform that's clipped as a result of the stator output diodes driving into a low-impedance load (the battery) and thus looks squarish. And when the amplitude is initially low due to low RPMs, since the tach signal isn't spending most of its time clipped, there will be additional noise due to whatever noisiness there is in the load driven by B+ (such as the starter motor), seen by the stator coils output, and thus also affecting the stator center point (tach output). Plus your scope trace will probably pick up ignition signals just by having the test leads flopping around and picking up electric field. :-) Anyhow, the putative primitive nature of that tach signal is what lends interest to how the ignition/start module treats it! It's already evident that the signal takes a hilariously meandering path on the PCB, before ducking out of view.

[@davidgrisco1939]

I'm left wondering if there isn't signal noise on one of the module wires that could be "encased" in a shield and connected to chassis ground to filter out.

[@TheCrazy243]

Sweet!! New video!

[@scruff_01]

Try a tach signal filter if/when you get a call back. Just a shot in the dark

[@disarm2k10]

What's the source of the tach signal? How can it be so noisy at startup? Could it be a simple ground issue and we are getting backfeeded from the alternator/starter?

[@PineHollowAutoDiagnostics]

The alternator produces the tach signal for this module

[@abdulb7178]

U r the best👍🏻👍🏻

[@aleskyfinis1025]

I see some imperfections in man from Aleskyfinis

[@robmut1357]

Yeah, I’m that type also. Questions that keep me up thinking at night. Hmm, what if I tried this... or maybe this... I hate loose ends.

[@rickjljr11]

do you think the tach signal is just one phase of the alternator? shorted diode in the alternator?

[@malkeetvirdi3582]

does this machine have an capacitor? i have a genie that wont start. to get it to start, i remove the wires from the fuel solenoid and contact them direct to battery, the engine starts and the the machine functions normally. what i found after having gone bald, the capacitor on TB41 was faulty. this is wired into the tach side. the machine i was working is genie z4525 model year 08. would love to get your feedback on this.

[@joshwilson849]

Ivan, can you tell me what power supply you are using and signal generator? Thank you

[@richardmckee9319]

If 1 doesnt come on should i assume the board is bad?

[@ZX14er]

The Grandkids will have to flip a coin: heads,,Penn State, tails,, Cornell.

[@gcbification]

I just want to see pictures of the module PCB....both sides.

[@Graham_Wideman]

Yes. Me too. I suggested that on the last video, but Ivan may not have seen that,

[@gcbification]

@@Graham_Wideman Aye, looks like Ivan's going to chase this rabbit-hole to the end, so lets hope we see those pics ~ a lot of electronics folks like you (I suspect =) & myself can divine a lot from seeing the circuit components/layout of modules like this.

[@Graham_Wideman]

@@gcbification Agreed!

[@PineHollowAutoDiagnostics]

I can post some pictures on the "Community" tab if people are interested!

[@Graham_Wideman]

@@PineHollowAutoDiagnostics Yes please! I'm sure all of us that have other work we are supposed to be doing will be happy to have an excuse to detour to this essential piece of reverse engineering :-).

[@northernpatriot9078]

Hi Ivan is it fair to say it is more or less a solid state problem and how module reads with algorithms it has

[@PineHollowAutoDiagnostics]

Well the module seems to not like the dirty rpm input from the alternator on start up...

[@real_arbuckle]

Bad caps are a plague on electronics from 1997-onward.

[@tenmillionvolts]

About the time people stopped paying good money for equipment and wanted cheap goods. So they get cheap caps. I work on Power supplies with 25 year old electrolytic caps, all OK. They just cost more. Also, you are supposed to throw everything away for the new model these days. Why do you need caps to last 25 years in a computer that can't even connect to the internet in 10 years time? It's all relative. You can now get solid polymer electrolytics with a huge lifetime. I've yet to have any fail at all. It all depends upon cost and expected lifetime. Sorry to rant but everyone seems to just assume caps can't last when they keep seeing cheap ones that aren't designed to last

[@mattmanyam]

@@tenmillionvolts there was a huge scandal in the electronic component market starting back then involving fake capacitors. This is what he was referring to.

[@jackpatteeuw9244]

SWAG - That particular module is more likely to see "noise" as a "signal" probably because the capacitor used in the filter of that input has aged and is now passing more of the noise.

[@VWWRENCHIE]

What is Ivan's favourite sitcom? "I Dream of Genie"

[@BobPegram]

GROAN!

[@7minnow]

Great Videos lov it keep it up!

[@Graham_Wideman]

19:00 Ivan: Nice! So what causes these noisy tach waveforms from the alternator? I'm wondering whether a dirty or worn slip ring or its brushes for the field winding in the alternator would result in an intermittent excitation field, and thus an intermittent alternator output including from the alternator tach output (that is a tap on the same output windings). Also, it's the voltage regulator that's supposed to be controlling the field winding, so an intermittent fault in the regulator could have similar effect, though I'm having difficulty imagining the details of such a regulator fault. It seems more plausible that slowly-rotating slip rings and brushes could exhibit this type of intermittency. Or indeed an intermittent connection from the battery (which supplies current to the field winding during starting) could also cause intermittent field current. But I'm still liking the slip ring or its brushes.

[@PineHollowAutoDiagnostics]

Great theory. Might be time for a new alternator soon, they do go bad. This one is probably the original and 20 years old!

[@throttlebottle5906]

i missed that it was a feed from alternator as tach. signal, the brushes are probably about gone in it then, they do get stupid noisy when worn way down. as they get worse it will make lights flicker and pulse on a vehicle, which seems to mainly be a ford thing, because I've seen it multiple dozens of times, in fact mines getting stupid on output not when first started and around idle.

[@MY-ml5rp]

@@PineHollowAutoDiagnostics Many years ago employed at a huge equipment dealer and the man lifts and genies, came into being ...starting was a big problem issue due to starting and stopping all day long. start it up ,swing it a little and shut it off. Adds up quick. Plus leaving the master switch on all night and the key on, or some one stealing the battery. Working in the dirt you will learn before you even check for a loose belt put on gloves,those edges on pulleys will get razor sharp due to dust and belts rubbing it in. Belts wear, pulleys get deeper. Caterpillars in the dirt those pulleys will slice right through you hand socks. Trying to remember if the nippendenso alternators were little like 22 or 35 amp if that is what is on your genie and the starting and stopping and worn puleys and going to full charge output and it is that critical for the tach sensor...my my my. maybe... Not knowing then what I know now from this experenice with you and the genie and trying to keep up with all of ,well its nothing new tech makes my mind hurt. I am very compressed with you skills and bull dog attitude toward finding the truth. Never got a whole lot of atta boys in my life but you deserved one. Atta Boy!

[@PineHollowAutoDiagnostics]

@@MY-ml5rp love the comment! I agree that the start stop running of these lifts is so hard on the engine and electrical system. Severe duty!

[@engeneer_ru5827]

@@PineHollowAutoDiagnostics Этому подъемнику 20 лет ?

[@sewing1243]

Can you find/get a theory of operation write up for that module?

[@PineHollowAutoDiagnostics]

Most likely it is a Genie secret 😎

[@somerandomguy3868]

Do you suspect a marginal tach signal/sensor, are you considering a new one? I'm wondering what a new tach sensor signal would look like

[@mattmanyam]

It looks just like a new alternator.

[@nevillegoddard4966]

Surely you've done quite a bit of electronics training Ive have you? What, with your own waveform generator & all? I'm a qualified elec tech so I 100% get what you're talking about.

[@Ivo--]

Hey Ivan, do you ever use the low pass filter on the pico to make the traces easier to read? I've always found it difficult to read the exact voltage otherwise.

[@liviu2004]

spankmeister filter and you lost the evidence.

[@PineHollowAutoDiagnostics]

I do when the signal is really noisy. But looking at the raw data first is always useful 🙂

[@Ivo--]

@@liviu2004 not at all, because the pico stores the original signal. You can play around with it all you want and never lose the original trace. 😁

[@liviu2004]

spankmeister you need to read the manual a bit

[@Phill22k]

So a lack of crank signal means letting the battery drop dead or cook your starter motor, Great design :-o

[@stephendee7839]

Exact same as most cars with ignition key starter activation (I e not start by wire).

[@arminprnjavorac2084]

Very cool video!

[@pb3033]

Is that a capacitor story ?

[@engeneer_ru5827]

Вполне возможно! In the photo of the board, the most vulnerable components are: C6 & C10. But they are for the voltage regulator MIC2951, it does not affect our problem.