A simpler way to test an oxygen sensor HD 1080p

[@LayZeeDawg]

Many years ago, as a youngster, I used my body as a resistor with an ignition coil. Lesson earned and learned

[@neverstoplearning382]

🤣🤣🤣🤣

[@davidparker9676]

@@neverstoplearning382 Your username makes a better reply than your emoji reply.

[@shawntailor5485]

My uncle used me for that resistor, he thought it was funny as hell but I think it was the beginning of a life long hatred for that prick.

[@yourworstfear]

hahahahahaah

[@davidparker9676]

@@shawntailor5485 Sounds like a cool uncle.

[@cybersholt]

Been working on cars most of my life and love how simple this tip is.

[@theserious1]

Craziest most ingenious thing I’ve ever saw in all my years of automotive work

[@gregjones8501]

If “thinking outside the box” was a person! So much knowledge from one person! I truly appreciate all you do to help us Dwayne! Hope all is well brother..

[@1b9e7n3z]

Another great class on how to use the knowledge acquired in math, physics and any other class that has to do with materials. You are my example for a long time.

[@confidential8738]

Old school tricks. Thats why i love this guy

[@highrev90homemechanic67]

This dude really knows his car mechanics Always great vids

[@paulfoldes3873]

good to see you again thanks

[@DM-rp7ps]

Wahoo - good to see you back! Keep up the good work doctor, am looking forward to the ones yet to come.

[@garyriggs8040]

Best explanation I have seen of an O2 sensor.

[@ThunderbirdRocket]

Re-visited this training tutorial … and gotta thank you once again for the fantastic coaching ! Super helpful !!

[@whtkngofc]

i used to have a beater car that had a problem cold starting, fitted a switch that shorted the map and 02 sensor, basically a cold start switch, worked brilliant.

[@ronaldmahoney1283]

That's a positive way to actually get the sensor to react! Thank You!

[@troubleshooter1975]

It is actually NOT affecting the sensor's control; the sensor signal has been overridden. The response by the sensor (if any) at that point is irrelevant... It is actually only confirming that the PCM can respond (and is in closed-loop)...

[@billrimmer5596]

Excellent teaching!! Really enjoyed it!!

[@luisvaldez6204]

If you are watching this... you are the Resistance!

[@unclemarksdiyauto]

Funny Luis!

[@luisvaldez6204]

@@unclemarksdiyauto because after watching this video you are going to be using your body as a resistor

[@unclemarksdiyauto]

@@luisvaldez6204 You know I will and I get the funny reference, Luis. Good comment!

[@juhajuntunen7866]

Resistance is futile!

[@Lou-eye]

Lol

[@topadrenalina679]

Thank you so much teacher tomorrow I will do this in the shop I really needed this I appreciate your help

[@timsinterwebs2936]

Great video and explanation of how to manipulate sensor values in order to see if the ecm is reading/responding correctly and how to confirm the sensor is reading in spec. Just one critique; never ever puncture a wire with a probe to access it. This will lead to more repairs and issues down the line. It is better to use a breakout harness or to back probe a connector from the harness to the sensor or from harness to the ecm. Thanks for the content, cheers!

[@JahanZeb1976]

Wonderful dear sir. Always looking forward to watch your awesome lecture. Always great work and perfect knowledge.

[@atomicdmt8763]

useful to move the torch up off the sensor and back on - after heating from the sides abit, I see in your video - and I just went thru a batch of O2 sensors just now. Many of my old sensors (I save everything) are fine! OBD2 scanner w simple graph to show B1,2 sensor 1 voltage movement is very useful info.... in closed loop. Thanks!

[@Geekdiymechanic]

I’m a little confused with test. How is this testing the o2 sensor? Isn’t this just testing sensor wire integrity to the PCM? Your o2 sensor could be dead as a door nail and this test would produce the same results. Maybe I misunderstood the premise. Thank you for the tips over the years. I appreciate the time you put into making a video.

[@darrenbradley6115]

I agree. The signal wire is from the sensor to the PCM/ÉCU. So by shorting it to ground or supplying it with a 1volt supply, all you are doing is taking place of the sensor and making sure the PCM reacts to the rich or lean condition. Your not actually testing the sensor.

[@daniellawson5127]

Glad I'm not the only one that saw that. Still makes more sense to add external fuel or introduce unmetered air. Even with no vacuum lines you can pull the crankcase breather hose off the intake. Supplying power to or grounding circuits should only be done with proper equipment, and id still typically advise against that. If the O2 is functional the PCM is going to make fuel trim adjustments but if you have low or high fuel pressure or sticking/clogged injectors it may not translate to what the engine is really going to get. I don't see where this "test" is going to provide any useful information to the technician. Doing stuff like this will end up resulting in a pcm being turned into a brick at some point.

[@ingejeppesen1358]

What he does is forcing the engine to go lean or rich, when he lets go he can then see if the sensor is working and will bring fueltrim back to "0". Instead of introducing a vacuum leak or introduce fuel he makes the engine computer do it.

[@AbuDujana692]

I fully endorse that this test can't verify sensor output...it verifies wiring/ circuit and pcm response to voltage/grd inputs....but then this video offering a quite unique way for verifying circuit & pcm response and its something which must be appreciated.

[@JohnSmith-xx1lx]

@@AbuDujana692 For sure lets not let that bad take away from the good, yes it's a wire test not an 02 test but a cool tecnique either way.

[@filimonpaz9122]

Excellent Instructor you are Mr.

[@realfixesrealfast]

Glad you think so!

[@ThunderbirdRocket]

Gold ! Pure Gold . Thanks .

[@DependableAutoTruck]

very good explained where anyone can understand found your channel the other day sure glad i did thanks for the hard work and i know how much trouble it is i tried have a couple videos uploaded i just don't have the time

[@jdcustomz]

The Human body is an Air and Liquid capacitor with an internal Antenna. Great video!

[@alexmessina3383]

Great as always, and clear and simple. Question: given most modern vehicles will be using a Wideband pre cat AFR sensor, can you explain how this test procedure might be applied in that case???

[@Anthony-tg9vs]

Wow ! Great video. Ive learned alot today

[@BjornV78]

You can also test the oxygen sensor (or also called Lambdasonde) on the bench with a DIY adapter. This adapter is just a short piece of metal pipe, with internal M18 x1.5mm threat, on the other side of this pipe a hose fitting. Then apply the necessary voltage to the heater, and connect with a hose (silicon) a vacuum pump, like those cheap brake bleeder sets. When the oxygen sensor is heated up, and the vacuum is applied, the output should be 1V , indicating a rich mixture. Inside a oxygen sensor is a capsule of Zirkonium that contains pure oxygen, when the outside of this capsule doesn't see much oxygen due a rich mixture, or a vacuum like in this test, the voltage will raise. During this test, there is no sinewave, but a more constant DC voltage between 0V and 1V, because the sinewave is created by the ECU due the mixture adjusting in closed feedback loop. This closed feedback loop is ignored during deacceleration (gas pedal not touched while the car is moving) and ignored for X time during acceleration when the gas pedal is pushed in quickly. With the vacuum, you can push the output voltage to 1V (or even higher) and to 0V if you could apply pure oxygen to the adapter, like from a oxy/acetylene torch.

[@paulwolf8444]

Yes, I repaired the original LAMBDA systems at a VOLVO dealer.

[@troubleshooter1975]

Mostly correct; the Zirconia 'capsule', which is actually a thimble or disk*, does NOT contain pure oxygen, but is supplied with atmospheric air, and is replenished through the sensor leads. I also discovered the manufacturers warn not to use any sealants or contact lubes on the connectors... *[edit: I found drawings that show the 'Planar' type as a flat wafer, not a disk, but I have not found details]. I applaud you for the creative test suggestion. You could also use any inert or fuel gas. Maybe propane or acetylene. (be careful...) [Don't mix oxygen and fuel gas in a pipe, you will have a pipe bomb! Vent/purge thoroughly in between...] If we could find out the spec for the O2 concentration at 'crossover', one could actually construct a rig to test for accuracy... One thing that it couldn't test would be response time, which I gather is the main issue with aging sensors anyway... Mr K L

[@EATSLEEPFARM]

Big brain stuff right here!! This is awesome!!

[@alank616]

Thanks for a great video easy to follow and understand 🇦🇺👍

[@StationGarageSt]

Useful knowledge thanks! The math behind it most interesting too.

[@CHIBA280CRV]

Another fantastic informative video 👍🏼👍🏼👍🏼👍🏼👍🏼 thank you.

[@notsohairybiker]

Fantastic short cut / time saver.

[@vincentlee2460]

I applied this on the wall socket and leant the lesson well.

[@mike-yp1uk]

As usual full of good info

[@javierjavier3458]

I understand that shorting to ground you generate a DTC on o2 sensor but, is any DTC when shorting to positive through your body? A part of that, did you test that way with 5pin o2 sensors the wide range ones? Thanks!!

[@troubleshooter1975]

I don't think so. Wide Band sensors have an output amp. You won't be able to 'override' it in this way. And if you did, it would likely damage the signal output chip. You could 'maybe' substitute a signal voltage to the PCM, with the sensor output lead DISCONNECTED. But the PCM also monitors heater temp and/or current, so it would be a technological challenge to do this properly... Propane or vacuum leak (to create a REAL AFR mix change), would be the most direct method to test a WB (A/F) sensor.

[@papimasfuerte4671]

This works on older models. Newer cars like Honda , bmw, use the amprage measurement from the oxygen sensor to adjust the trims.

[@unclemarksdiyauto]

I very useful test I am going to have to try out. Thanks!

[@vin605]

AMAZING 👏 thanks for sharing

[@W.Khairi]

Great tip, Thank u very much.

[@spelunkerd]

The first time I saw Scannerdanner do this, I had an aha moment. I only wish I could find a way to similarly test wide band sensors and their wiring.

[@jimpetty2961]

here is another good teacher for all of you to subscribe to.

[@jamesd6247]

Is this really testing the sensor or just manipulating the signal to the computer and testing the ecm and wire integrity?

[@fredsalter1915]

@@jamesd6247 I'm suspecting the same thing.....

[@paulpaquette1961]

@@jamesd6247 This does not test the sensor. All this proves is from the point he tapped the O2 Signal wire to the PCM , that the PCM is capable of "seeing" a high or low voltage. This proves Wiring integrity only from the point of tapping to the PCM. When possible and accessible we do this test to prove we don't have a signal wire problem, I prefer to do it right at the O2 connector disconnected and frontprobed with the proper AESwave adapter. Drive it high then low. I will use th raw 12v from a testlight to drive it high. The pcm is programmed not to "see" over 1 volt, but you can still put more, using a testlight puts a buffer in case of a short to ground, in which case the lamp will light!!!. Now that Wiring Integrity has been ruled out, you still need to physically alter the Air/fuel Lean or Rich to see if the Sensor is capable of producing the proper voltages. And another thing to consider is the Heater circuit could be week and make the signal to appear lazy!!! This video has a lot of truth, but is kinda misleading. Peace.

[@rupe53]

@@paulpaquette1961 ...yes, but once things are warmed up the heater is out of the loop. The heater is only for the first few minutes of operation to get things into closed loop faster.

[@paulwolf8444]

I have been doing this since the early days after VOLVO introduced the original LAMBDA system. LAMBDA meaning AIR. Back in the day there were no fault codes or scanners.

[@jessev2197]

Wow. This is such an old skool thing. I used to do this back in the 80s. Not many cars use a 1volt sensor anymore. Won't work on wide bands.

[@deyantodorovski4805]

Bravo Maestro!

[@domingodeanda233]

That was pretty damn good, thanks

[@damxgopak457]

Great information thank you I have a sensor on my suburban that is nearly impossible to access.

[@trsfc1595]

Very informative Thank you

[@friendcars1711]

Thank you 😊

[@rrangana11]

Excellent video on testing O2 sensor. Will this also work for Air Fuel Ratio sensors?

[@bennyblanko3]

You are a smart dude!

[@Splashfun2000]

Where did you get that little tool/connector to tap into the wire ?

[@papimasfuerte4671]

Love this guy

[@richardjones3112]

Great video.

[@GRAZINGARIZONA]

Will this work for all o2 sensors (4.7 iforce toyota specifically). My sister in law has changed several recently and still gets code. She wants to swap again but I'd like to actually find the issue. Thanks.

[@paulromsky9527]

Nice tip on using your body as a variable resistor. But I strongly caution: Even though you are only working with around 12 volts, passing ANY current through the chest, even far less than the deadly 0.1 A (100 mA) is NOT wise. Even a few milliamps passing from one hand, through the chest, and to the other hand CAN be dangerous. Even low current through your heart may not cause instant death, but it can cause "walking wounded" damage to your body. Ask any electrician, you use ONE HAND ONLY when working with any voltage/current - this way current passes through your hand and not your heart/brain/organs. I would suggest you get a 1Meg Ohm potentiometer (Pot) and a 10K (or whatever resistor value that forces about 1.2V on the O2 Sensor signal when the Pot is sent to 0 Ohms). Put them in a liitle plastic box with wires and alligator clips. You get all that from Digikey for about $15 and you made a nice O2 Response Testing Tool for your arsenal of tools and do-dads. 12V | | o | | 10k Ohm (or other) Resistor | o | o | | 1M Ohm Pot |

[@dannyh773]

Think about it. Wires good. What’s left that can be bad. I’ve seen other videos do this. Also used to be a tester that did this to check wire connection. Do any of you remember the old condenser prank. Now that was a shock. 😂

[@Truthorshit]

good show!

[@shamessun]

Thank you very much

[@robertfoilesjr1337]

It sounds like this is a good bypass test for circuit integrity but bypasses the sensor so does not test it in any way. Let me know if I am misunderstanding. Thanks for your content. Very helpful for scope Verus learning. More please!

[@fredsalter1915]

I agree. I'm not an expert either, but you could artificially introduce voltage or ground to the PCM and the scan tool will read whatever bypass voltage/ground you supply. Color me skeptical.

[@craigwillers6400]

I agree, what he is doing there is testing the integrity of the wiring and pcm but not the actual sensor

[@geologic740]

I think what he's trying to say is the circuit itself is tested as you connect to ground or positive through your body and see the extreme readings and fuel trim. After you remove your tap from the wire or plug the sensor back in, the sensor is proving that it works correctly when it readjusts, oscillates and the fuel trim normalizes

[@fredsalter1915]

@@geologic740 I'd rather force the sensor high and low by vacuum leak and propane addition and watch the oscillations. That seems more definitive to me...

[@ThunderbirdRocket]

Can you tell me about the concept/theory you are considering - the bypass . Why do you say that he bypassed the sensor in the procedure he demonstrated in the video . The sensor remains in the circuit .

[@k.y22]

👍thanks sir .

[@train4905]

Brilliant sir

[@MrDeviousdom]

You can totally connect 12 volts right to it without an issue. Put it through a test light as a current limiter.

[@garygatten1154]

Is this really testing the sensing element and voltage generator? Seems like you're bypassing the sensor, injecting an artificial signal to the ECU which adjusts fuel trim. I'll watch it a few more times, I probably missed something.

[@georgeh1352]

I'm having trouble understanding how the O2 sensor produces a sine wave. I know Zirconian substrate poduces a 0.1 to 0,9 volt against the differential of clean Oxygen side to the contaminated Oxygen side of the substrate, but I would expect to see a DC voltage output. Where am I going wrong?

[@bbeauregard4181]

Excellent!

[@paulrunell7821]

is this test ok for wide band and narrow band

[@realfixesrealfast]

the video is on narrow band. It works for wide band but the interpretation is different

[@nas979]

I couldn't Resist but to watch this video

[@shinola228]

That's interesting but how do you recognize the signal wire ? Thank you.

[@larryreno8293]

It was identified by using a wiring diagram. The wires are color coded with a tracer color as well.

[@michaelgunning347]

Forcing a signal wire to ground , dose not prove the sensor can read lean it simply prove from that point back to the ecu is correct

[@francpez7564]

Can you show us a diagram of how you are shorting it to ground and supplying 1 volt to it? I'm a little confuse here. Thanks.

[@Jordan__Sloan]

Hey thanks!

[@treadaar]

You are not testing the oxygen sensor though, you are only testing the ECU response to the voltage which would come from a WORKING oxygen sensor. Title is wrong, still an interesting video, it just doesn't do what it says on the tin.

[@arvindtaylor6871]

Great video. Why are not seeing anymore new videos. I’m missing them🥵

[@iwankennis9699]

Thank you for this great demonstration. But you said that in this way you tested the sensor. But is that really. Because I think only manipulate the signal and test if the pcm responds. With this test you can't say that the sensor is working correctly. Because it can still give wrong signal depending on mixture. Let's say it's producing a to low voltage for a specific mixture. If you this test, the pcm still will react. So this test will not condemned a not good sensor

[@emil.honganmaki5461]

First of all, the car battery is completely safe without any resistors..and a simple voltage distribution circuit, i.e. even if a 1000 ohm resistor is connected to a 100 ohm resistor, the voltage enters the 1000 ohm resistor and goes to ground from the 100 ohm resistor, so the poles of this 100 ohm resistor get about 1v, so it can be adjusted as desired.

[@rupe53]

If we hooked into the front sensor and did a voltage reading during these tests we'd know if the front sensor was working.

[@manuelborja101]

Gracias

[@Navajo329]

thanks

[@age_of_reason]

Humans have mastered their environments to such a high degree that we can calculate the exact effect of touching a positive battery terminal and have it displayed on a screen. Human: Silly little laws of nature. 😂

[@simonilett998]

The o2 sensor itself didn't 'recognize' anything whatsoever from this method you showed? The only things this proves is that the ecu could recognize a min max range it's programmed to the able to see, on the o2 signal wire, from the position you were tapped into. This only proved that the ecu was capable of making an attempt to compensate for the false rich and lean conditions. The one other thing this test proved, is that the wire is intact between the ecu and your tapped in test point. The only relationship this test has to the o2 sensor, is that once you removed your false rich/lean conditions, the ecu stopped making false compensations and was able to bring the o2 sensor back into a normal switching range, short term trims came back within an acceptable range, but at no point did the o2 sensor itself 'recognize' or 'sense' anything apart from exhaust gas oxygen levels, the O2 sensor makes voltage and sends the voltage signal to the ecu. The o2 sensor doesn't sense a voltage on the signal wire at all as you inferred by saying the o2 sensor 'recognized' the increase or decrease in voltage induced by your method..wtf? You were simply shunting the o2 sensor signal wire to ground, or driving the voltage on the signal wire high before it gets to the ecu, the ecu is what actually 'recognizes' a signal, and makes compensating fuel adjustments based on the signals it receives from various sensors. Sensors create and send signals, they never receive or recognize anything. Receiving, recognizing and interpreting is a job for the ecu, and/or various control modules, never sensors.🤣👍

[@jimmuehlberg2153]

Agreed. This also told me that the circuit impedance is very high. Skin resistance can vary wildly and unless you are soaking wet or sweaty, the resistance through your body is probably 1000's of ohms. In any event, his body and the input resistance to the ECU made a voltage divider that produced a 1 volt reading. It is likely "clamped" at 1 Volt at the ECU to protect from over voltage anyway. I suspect using a 10,000 Ohm resistor instead of your body would produce the same result. (start high and don't go lower than a few thousand Ohms if you try this!) What this video did make me realize though, is that the connector needs to be very clean - no lubricants or oil or whatever. A little stray resistance in there and you'll be all over the map. I think this is whats wrong with mine!

[@SEDHACARREPAIR]

What will happen if signal wire shorts out to power

[@realfixesrealfast]

depends on the strength of the voltage power and purity of the ground. The worst case is a blown fuse, less severe would be distorted signal.

[@richardcranium5839]

forgive me for not understanding but these tests only prove out the circuit. you are altering the signal even though the a/f ratio isnt changing. how does this prove out the actual sensor??? i would think the a/f ratio the sensor live in would need to change to actually prove the sensor.

[@hotratz69]

I don't see how using human skin will give you repeatable results. I have measured my resistance through my finger tips many times through out my 45 yrs as an industrial electrician. And depending on a LOT of variables. Humidity, skin moisture, surface cleanliness, presence of callus, blood salinity and mostly probe contact pressure with skin. I would get vastly different values each time. I would think it would be better to use a fixed precision resistor to use as a reference. Much more repeatable and safer.

[@troubleshooter1975]

All the critical comments below are true: Your logic is flawed; You are testing only the harness and PCM (injectors, MAF, etc - closed loop components, EXCLUDING THE O2 SENSOR!) With the sense lead grounded, the O2 sensor could be good, bad, or missing; and you would get the same engine response. Likewise when you induce a voltage. You are NOT testing the O2 sensor response whatsoever... Also, I am baffled by your O2 current calculation. It doesn't make sense. Were you proposing that the O2 sensor has an internal resistance of 1KΩ? The sensors are very high impedance AFAIK... The math doesn't relate to anything you were doing. I can only speculate that you were thinking how much current would go through YOU if you were grounding the sensor to ground. And that calculation would only be valid for source impedances less than a few hundred ohms... Also, the figure of 1KΩ for body resistance was from a safety chart, and is worst case scenario. Typical body resistance is around 10-50 KΩ range. (try it with your ohm meter...) I commend your efforts though, you just misinterpreted the results. This would be a good way to rule out an expensive PCM replacement... (If it failed, it would not necessarily mean the PCM is bad though, there are other things could kill the closed-loop operation). Mr K L

[@jinxxpwnage]

With my luck, this would take me clean out

[@farrukhawana.r.a.q9194]

You should use mic for this video

[@robotexplorer]

i dont see how this tests the o2 sensor. You're manually forcing a voltage to the PCM and forcing fuel trim changes.

[@eyeonart6865]

I took mine to a mechanic and they said my downstream 02 sensor was shorted out and they changed it after having my car three weeks. and my car still showed po 301 which is why I took it to them. so I called a mobile mechanic and watched him and he unplugged the up stream sensor and showed me this yellow oily stuff in the plug. he cleaned the plug and changed out the 02 sensor. Now I do not trust first machanic. I will use my mobile mechanic because it did not bother him having me watch him.

[@82_KID]

Resistance is futile.

[@bowez9]

This doesn't test the Oxygen sensor but the ECU response to sensor signal. If the sensor is physically failed this does nothing.

[@thadrepairsitall1278]

This is an old school trick. It probably doesn't work well on newer cars.

[@j.robertvillarreal5926]

What a waste of time. I am an L1 tech and it is easier than this. You drive it rich and watch the fuel trim. See if it responds. If fuel trim responds you drive the engine lean. A small air leak is fine. Does the computer see it and react. Your fuel trim will show that. If the PCM responded to both conditions it means the PCM is in control. Next Go and the put the Scan tool in graph mode and put the time span equal to injection pulse width. Remember, this tests the sensors before the CAT. Your signal will look like skyscrapers. Each square is an exhaust pulse. Check the voltage range by the manufacturer. If you have leaning signals like a lean-to or a barn roof this is called clipping. The sensor is bad. If you are checking the O2 sensor heater just use active testing. You CAN test this out of the exhaust system. Just tell the tool to heat up the O2 sensor and hold it. It will get hot. Easier than this, check failed monitor tests. To see if you have a bad CAT. Go to graph mode and put banks 1&2 over the CAT Sensor. Look at the signal going in. Should be square waves going in the CAT, and a small fluctuating line with no square waves after the CAT. The rule of thumb is 140-160 cycles unless specified by the Manufacturer. This is for the O2 sensor that watches the CAT. The signal will look like a small harmless wave or a flatline. Flat line is good after the CAT. Harmless wave means okay to CES or SES light soon. When the wave before the CAT is about the same as after the CAT. Your CAT spent all 9 of them. We have not used this method of using yourself as a resistor in 20 years. Time is money.

[@STRANGE_hour]

Yeah duh obviously

[@ahmedabdelfattah1939]

How about You yes YOU MEASURE YOURSELF FIRST WITH DMM before touching B+

[@jyao5409]

I am sorry but this is not a test for the o2 sensor. This is a test for the o2 wiring integrity and ECU logic.

[@davidknightaudio934]

couldn't be more wrong silly old man

[@Lure-Benson]

I have owned a 1 ton 1988 Chevrolet Truck with 454 that constantly was a pain with the computer system & oxygen sensor so when the 454 had been wore out the next engine I put in was old school no computer system at all on the 383 stroker engine. Living in Alaska where I often travel then can't get help, I don't need a truck with constant computer system issues.

[@fieldsofomagh]

Glad to see you're still on de prairie trail to californie and fixing dem combustion maachines. 🚘🚗🚙🛻🚓🚕🚜🚛🚚

[@whitehorse1959]

🔌

[@nickayivor8432]

ErictheCarGuy was right about Realfixesrealfast SUBSTANTIAL Realfixesrealfast My teacher Thanks 👍 From start to finish loved it thank you very much helpful information video Take care and have a great Evening with all your family around you SUBSTANTIAL Realfixesrealfast From Nick Ayivor from London England UK 🇬🇧

[@rick-kx7gy]

Not to judge or confuse here but with the engine running the positive voltage is closer to 14.2 volts than 12 because of the alternator charging .