How to test capacitors and troubleshoot for HVAC

I cover run cap testing, start cap testing, hard start kits and measurement of cap strength for air conditioning and heat pumps.
This video is part of the heating and cooling series of training videos made to accompany my websites: www.graycoolingman.com and www.grayfurnaceman.com to pass on what I have learned in many years of service and repair. If you have suggestions or comments they are welcome.
If you are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. Know your limits.

[@trevorhanlon471]

Thanks,nicely presented in an unbiased,un egocentric,easy to follow manner.

[@robertviejo9048]

love your videos. I'm in hvac/r school, and my teachers don't get nearly this close to teaching. Thanks Grayfurnaceman. My career will be brighter because of people like you on youtube!!!

[@grayfurnaceman]

Thanks for the support. GFM

[@pigley14]

Very wonderful video. Currently chasing my degree in HVACR. Being that I am on Winter break I am using your videos to make sure I stay sharp on my knowledge for next semester. Thanks for posting.

[@grayfurnaceman]

In some companies service departments lose money, but as a service tech I think they can be profitable. The HVAC industry is not a high profit business, (3 to 5%) of gross overall. GFM

[@grayfurnaceman]

Probably not a better teacher, but I just said it in a different way that works for you. Thanks for the comment. GFM

[@grayfurnaceman]

In this case, the caps should be mounted in parallel. I will do a video on caps in series and parallel. Thanks for the comment. GFM

[@grayfurnaceman]

Thx for the comment. Someone starting out in a new business needs to get the services of an accountant and find out what the real cost is. When you charge $100 you don't take that home. You will be amazed at where it all goes and if you charge too low, you will not be happy and you won't be available when the customer needs you again. GFM

[@dpeagles]

Yeah I haven't worked fulltime in HVAC since 2004. May be why my prices are low. I just notice so many techs undercharge for their service. It costs a lot to run an HVAC business so don't feel bad for charging a lot. Anyway, I done hvac for 15+ years and I have still learned a few things from you videos. Keep up the good work.

[@EddieLeverich]

I've been to plenty of customers who paid to have a hard start installed only to have the compressor go bad shortly after. Like he said hard starts are not repairs Good video!

[@mountainman875]

Thanks for all of your videos. You just helped me fix my 22 year old Carrier furnace (bad control board).

[@grayfurnaceman]

+Patrick McFadden Welcome GFM

[@dpeagles]

Agreed. Kind of like just adding refrigerant without finding and fixing the leak. You had to be very clear. Note it on the invoice and have them initial.

[@freewoodencrosses]

At 11:39 the capacitor read 7.28 which is in tolerance for the 7.5 micro farad capacitor with a tolerance of +/- 6%. It could read as low as 7.05 and still be in tolerance.. or It could read + 6 percent or 7.95 micro farads and be in tolerance. Very informative video ,... I'll bet you have changed a lot of HVAC capacitors... The bad ones I see are puffed up, but not always.

[@erok562]

your a better teacher than my teacher at the college I got to

[@grayfurnaceman]

Markups for parts of this cost are around here are 3 to 5 times cost. This may seem high, but warranty replacements include parts and labor and a cheap part may cost a lot in labor. My advice to you is to call the company and take advantage of the warranty. A good company will want you to come back for all your repairs and poss replacement equipment. Even if the repair is out of warranty, the service manager will usually listen and may cover all or part of the repair. be your own advocateGFM

[@AdamSteidl]

Thanks, Gray Furnace Man. God willing, my A/C will keep keep running. Got a Dometic BriskAir on my RV that stopped working for a few weeks, was okay when FL got cool for a few nights, but the last few days.... Thanks again. Useful knowledge, I hopefully won't have to learn again, lol.

[@robertbl6983]

I LOVE THIS TYPE OF EDUCATIONAL VIDEOS THANKS SALUDOS PA MI JENTE AND REMEMBER ONLY YOU CAN PREVENT A FOREST FIRE.

[@stevethomas8144]

Think you taught me more in this 15 min vid than my instructor in college did for 2 weeks lol.. Thank you for posting this :)

[@georgechambless2719]

Excellent video! I am having problems with my AC compressor and this answers all of my capacitor questions. Long live KZbin!!!!

[@grayfurnaceman]

I always wrote on the invoice that it was a temporary repair. That way (hopefully) you did not get called a ripoff artist. And there is a difference between a "fix" and a repair. I have had that fix work for as little as 2 days up to 2 years and tell the customer just that. Thanks for taking the time to comment. GFM

[@grayfurnaceman]

As for voltage, you can go higher but not lower. As for strength, you can go higher or lower by 20%. The 5 microfarad is well below the 20%. Lower strength will cause the motor to start with lower torque (perhaps not at all) and run unbalanced between the start and run windings. Probably overdraw of power. Hope this helps. GFM

[@grayfurnaceman]

I know you are supposed to do it that way. Exploding cap, damage to the cap etc. Then I looked at the wiring for the motor that the cap is connected to. The resistance of the motor windings that the cap is connected to is less than 10 ohms. In addition the cap discharges 120 times a second during operation.. So until I have definitive tests that can convince me, I will not worry about it. GFM

[@rasmussen667]

i got the idea from one of those high dollar caps you had in one of your previous vids years ago i salvaged it and went directly to the outside of the box :)

[@grayfurnaceman]

You just touched my pet peeve. If a service tech has not charged all his time, he is only cheating himself. Drive time and phone time should be charged to the job or if not possible to the company. If a company requires you to be someplace at some time they are required to pay you. The only exception is if they are paying you flat rate. Flat rate should be only considered if you are getting a competitive rate including down time. Don't give away your time!! GFM

[@grayfurnaceman]

If they are within 20% of rated, they are ok. My guess is its bearings are failing or there is a shorted winding. If the blower turns easily with no power on it, the bearings are ok and the windings are bad. If the bearings are stiff, you can try oiling the motor if it has oilers, however the bearings are probably damaged and the motor will not run for long. Hope this helps. GFM

[@grayfurnaceman]

If you mount them in parallel that will work. If you mount them in series the strength is the reciprocal (long word). It means if you have 2, 5 MFD, it will equal 5/1 or .2 MFD plus .2 MFD or .4 MFD. So generally mount them in parallel and add the cap strength together. I will do a video about this operation. GFM

[@gatesmw50]

When I went to refrigeration school, that relay in the hard start kit is called a "potential voltage relay". The relay is supposed to remove the capacitor out of the circuit at some point during the compressor startup sequence. It provides a "kick" to the compressor to get it running. If that relay sticks or is shorted closed, and does not drop the capacitor out, the capacitor will blow and fail just like where he is showing that hole in the top. A start cap is NEVER meant to remain in circuit, unlike a metal can run capacitor. The principal for how the start relay works is called "back EMF" (electromotive force).

[@grayfurnaceman]

Well, I have climbed inside the unit and lifted it out. Of course, it would always be better to have help. There are lifting handles that can be used but I don't think they work on Trane. Hope this helps. GFM

[@grayfurnaceman]

Well, it might. They have to be able to withstanding the back EMF in the windings. Back EMF is stacked on top of input voltage. I tend to replace like for like because only the manufacturer knows what will work. GFM

[@patrickr9862]

i go to refrigeration school and i always learned that an OL reading between the 2 terminals on the capacitor meant it was good, and any measurable resistance means it's shorted.

[@grayfurnaceman]

An OL reading means the cap is open. When testing a cap with a digital meter, you will need a meter that has a capacitor tester built in. GFM

[@Zionsol777]

one thing you may mention for those not experienced using meters, especially digital ones, is if you measure and open circuit it is a good thing to short your meter leads to ensure you don't just have and bad lead connection etc. also if measures open, it may be charged in that polarity already, swap your meter leads and ensure reads open that way also. just sayin. cya

[@grayfurnaceman]

Todd Pierson Thanks for the thoughts. GFM

[@mmichaeldonavon]

Hey, thanks for the information - like the gfm says, we are always learning; that's what makes it fun!

[@sivalley]

One correction you may have posted somewhere in the chain of comments; start caps are 100's of uF, most commercial capacitance meters stop at 100. OL means Over limit, not open. To test a start cap proper you need to use a clamp meter and measure in rush / running currents. Ratio of more than 75% of LRA means bad cap.

[@grayfurnaceman]

Thanks for the support. GFM

[@mmichaeldonavon]

Nope! Didn't know that. You caused me to research these giant capacity caps, and I found out that a company called "Maxwell Technologies" makes caps in the 3000 to 5000 Farad range - wow! :-) Low voltage, apparently, but extremely high current. And additional current is what we are always looking for to create large magnetic fields, to enhance torque in massive motors, etc. Thanks for your info.

[@grayfurnaceman]

Most run caps have no indication of polarity anymore. Originally, they were marked with the internal plate that was closest to the outdoor can for the incoming power so if it shorted it would kick off the circuit protection if it shorted. The short of it is it probably does not make any difference. Hope this helps. GFM

[@grayfurnaceman]

Are you sure it is not labeled? Many of them have the info printed on them. You can check with the manufacturer. If you can't find it, and the unit is inoperable, you will have to guess. Compressor run caps are larger for larger and newer units. The range runs from 20 MFD to 50 MFD. If you choose incorrectly, the unit will probably run for about a month then the windings will fail. Not good news but if the unit does not run, the only choice.

[@grayfurnaceman]

Thanks for the comment GFM

[@grayfurnaceman]

The OL designation can mean outside of the capacity of the meter or an open circuit in a resistance circuit. Which is outside the capacity of the ohmmeter. So it can be confusing. I use a Fluke 16 multimeter and it reads over 200 MFD so I have never seen the problem you describe. Interesting comment. Thanks for the thoughts. GFM

[@grayfurnaceman]

Thx. Sometimes its good to see it another way to make the connections. GFM

[@grayfurnaceman]

Try rotating the blower wheel manually. If it turns hard or not at all, motor bearings have failed. If it turns easily, it may have a capacitor failure. Hope this helps. GFM

[@dpeagles]

At my old company we would charge 120 for a regular dual cap. Seems high but this was for part + labor + warranty. It seems that no matter what you charge they may complain. I have given away stuff to some customers and they still complain about the price.

[@sivalley]

I hope I didn't mean to come off sounding condescending. Maybe I SHOULD go to bed at or before 2. But yes, Fluke does use OL in ohms, and ohms only, to mean open. In capacitance mode it means it simply is out of the meter's design testing range. Only very small start caps are less than 200uF. Most I've encountered are 300-400 range and one was 650! The fluke will indicate a shorted cap by reading "0", whereas an open cap will show a drifting reading from stray lead capacitance.

[@hashyfingers420]

The AC had been hooked up to an outlet that was piggybacked wrong with power hooked up to lower posts and coming out the top. I replaced the outlet and corrected the wiring and tested the outlets.

[@rasmussen667]

gray i have used a cap trick that has saved my but a couple of times wanted your opinion sometimes your way out in the middle of bfe and you need like a 15 micro ferad start cap and guess what you dont have one so i will take 2 _7'5 or a 5 and a 10 and as long as the secondary voltage is the same i will wire them in series i believe is the term they will test right and operate the motor without effecting. the rated amp draw on the motor

[@grayfurnaceman]

You know, I never have. I guess its that if it is shorted to the can It will either kick off the circuit protection, show an abnormal strength reading or burn up the cap. Anyway, good thought. You might find a problem before it actually fails. GFM

[@grayfurnaceman]

I would expect that a service tech should make an honest buck without overcharging. I mean we are talking about a $15 to 25 part. If you are using an Amrad, $45 to 50. Not telling you what to charge not knowing your location etc, but still, GFM

[@grayfurnaceman]

The other side of the argument is the poor quality in newer caps. I know one company that will install nothing else because of common failures. Whatever works for you. Thanks for the thoughts. GFM

[@grayfurnaceman]

If the blower humms, there is power to it. Spins freely, cap is ok and motor humms, I would have to say the motor has failed. GFM

[@grayfurnaceman]

The meter is set on MFD. You need a meter with a capacitor setting. I have done some comparisons of meters on the grayfurnaceman web site. That may help. GFM

[@defaultuser000]

The DC resistance(what an ohm meter reads) may only be 10 Ohms but with the AC current at 60Hz the AC impedance is higher than that. Also with the cap discharging at twice the mains freq(120Hz) that's still an extremely slow charge/discharge rate compared to placing a screwdriver(Probably less than 0.1 Ohms) across the terminals. I used to do the same thing until I had a cap explode in my face because I exceeded the discharge current rating by about 10,000 times when I shorted the terminals.

[@grayfurnaceman]

Hope the cap works. Bet you will remember the filter in the future. GFM

[@grayfurnaceman]

Always go higher on voltage. The 250v may short. Hope this helps. GFM

[@grayfurnaceman]

They are probably using the amrad. I know of some companies that use them only because of warranty failures with oem. It does seem high though. GFM

[@fredmullen585]

Your video on capacitor testing helped me find the problem with my fan not working. Now I cant determine what polarity the capacitor I took out is. The wiring diagram only says which color wire goes where, but the where is only indicated on the diagram by a "red dot." It does not say what polarity the "red dot" indicates. The capacitor is rusted, so no red dot is visible. Do you know what polarity the "red dot" is? It is a Ruud.

[@tekdro]

Testing capacitance that way is spotty. Many times I have seen capacitors test within range according to the voltmeter but still do not work under an actual load. This is because this test only puts the capacitor under the load of your meter's 9 volt battery, which pales in comparison to a 420 volt load of a compressor. The only method I rely on anymore for an accurate microfarad reading of a run capacitor is taking a voltage and amperage reading with the system running so the capacitor is under a normal load and plugging the readings in the magic capacitance formula of AMPS x 2650 / VOLTS = MICROFARADS. To obtain the correct amps and volts measure the amp draw on the wire from the hermetic terminal to the compressor or from the fan terminal to the fan motor. Then the voltage from the 2 terminals of the capacitor (or on a dual capacitor with 3 terminals, COMMON (C or COM) and HERMETIC (H or HERM) for the compressor or COMMON and FAN (F) for the fan motor). If you cannot test it under a load because the motor or compressor will not start or run and they are wired properly and not in thermal overload (overheated), chances are the capacitor is totally dead. In this case your meter will probably verify this on the microfarad setting, but I typically just go ahead and try replacing it with a new capacitor rated for the same microfarads and the same or more volts and start the unit again, and voila, she's usually restored to her former glory.

[@grayfurnaceman]

I don't know if I have this right or not. I tested this on an air conditioner. My numbers were as follows: Fan, .4 amps X 2650 = 1060/ 344.1 volts = 3.08 microfarads. Listed cap size = 5. Compressor, 8.5 amps X 2650 = 22525/ 363.3 = 62 microfarads. Listed cap size 45. Tested both. Fan came out 5.15, compressor 45.4 Let me know what you think. Will be doing a video on several units to test this. GFM

[@grayfurnaceman]

Is your ac on a dedicated circuit? If not, there is no way to isolate the problem without amp draw reading. I would be using an ammeter on the breaker. GFM

[@grayfurnaceman]

Start caps are not especially accurate in their capacitance. ESR is not something we check. When compared to electronic capacitors, our needs are much simpler and if the cap will release enough out of phase power, the compressor will start. Usually if it does not start the compressor, we replace it. Generally no damage to the compressor occurs. Hope this makes sense to you. GFM

[@kurtwm2010]

I replaced the cap and contactor module on my home condenser because the circuit breaker trips periodically. Replacing these two parts did not help. The thing runs fine for 2 or 3 days and then suddenly the breaker trips. I reset it and it's good for another 2-3 days. Checked wiring to make sure nothing is burned or corroded and checked for clean coils, but it all seems fine. I can't determine whether or not the breaker trips while the fan is running or wants to start running. Any hint you can give me to narrow down the problem? btw...the condenser is about 8 years old. I am considering installing a hard start kit. Can such a kit be harmful to the compressor if it is not needed?

[@grayfurnaceman]

Don't bother with the hard start. Tighten the terminals on the breaker. If loose, they can heat and kick the breaker. If it still does it, replace the breaker. Hope this helps. GFM

[@tommyweston8622]

compressor could be drawing too many amps on start up try cleaning condessor

[@joebriggs9599]

Thanks you saved me from getting a large bill.

[@grayfurnaceman]

+Joe Briggs Welcome GFM

[@daimlerblanco4534]

I can't believe some people dislike this video but that's ok maybe they aren't interested in this field

[@grayfurnaceman]

Yes, more expensive but work well. GFM

[@grayfurnaceman]

Take pics before and during the job. Makes it easier. GFM

[@hashyfingers420]

great video! Here is the problem I'm having with my window AC. It trips my breaker when i turn it off and doesn't trip it if i unplug the unit.

[@grayfurnaceman]

Glad I could help, but don't quit college! GFM

[@jordanhorvath1440]

excellent videos! keep it up

[@geojor]

when a capacitor is connected between the start winding and run winding of an induction motor, what cuts the start winding out of the circuit?....thanks...

[@mattthomas4026]

Here's a question for you. It's HVAC related. I have a window ac unit. The unit has really basic settings. 1 through 7 for how cold. High fan low fan. High ac low ac. The unit is 7 year old GE. It only works on #7 for the temperature and on low ac. Just started doing that this summer. I'm curious to what happened. I'm not sure if I want to try and fix it. I've been told Window ac units are cheap and the parts are expensive to replace

[@benvilla2378]

Great video!

[@jklesney]

Excellent video. I'm testing a start cap that looks identical to the one in your video. It has no labeling and with the 16K Ohm resistor disconnected reads 151 MFD. There are no markings on the cap, how do i know if 151 MFD is the correct (as-designed) capacitance?

[@amandafeenerstaff1276]

Have you ever seen a Run cap in the condensing unit cause a short in the low voltage cct? Perhaps one that is 45 and 5 dual run cap when it should have been 50/5uf. Blow a 3a fuse on the furnace ctrl board and smoke the thermostat?

[@grayfurnaceman]

No. They are completely separate circuits. Look for a short to the chassis in the wiring. GFM

[@ronaldwest2811]

grayfurnaceman ö

[@grayfurnaceman]

Hope it helped. GFM

[@40wyattearp]

I have a question. I have a 300vac 10uF capacitor on a fan. All I can find to buy is a 250 vac 10uF and a 450 vac 10uF capacitors to replace it with. Which do you think would be best.

[@flightmaster178]

Gerri577 I do a lot of fan work, I've never seen a cap go bad yet but most of the time there's a thermal fuse internal to the motor (inside a sleeve) that gets hot and opens the circuit. You can check a cap by shorting it, then ohm it out you'll see resistance increase higher and higher then your meter will read I or OL etc. then let it sit for a few secs then check resistance again it should still retain the power. Then you can short it out again and do it again bit yeah. Also, I'm credible I work on avionics and wiring on F-16's (~30 mil a piece) I've been doing this stuff a while and we learned about all this in school and have college credits for it :)

[@grayfurnaceman]

I did a video on the method you have described. It works but what a pain. There are so many meters with the capacitor tester in them that I always use them. Capacitors have had a low failure rate for many years. But now I can't say the same. The Chinese ones have had a very high failure rate. Thanks fore the thoughts. GFM

[@grayfurnaceman]

***** We actually have a lot of problems with the newer Chinese capacitors. GFM

[@flightmaster178]

Yeah as far as I know, these jets don't have Chinese capacitors lol. Although, I hear about a lot of TV's that are dying because the caps keep bulging and frying up easily just after a couple years of service.

[@SirSmokesAlott]

thanks gray, very helpful.

[@brads215]

Hi GFM. I am learning a lot and enjoying your videos. Is your meter set on ohms? I want to buy one, but I don't know whether I need a meter that includes a "mfd" setting.

[@grayfurnaceman]

Any more virtually all digital meters have a capacitance setting. Digital meters won't work for capacitance if they don't have a capacitor setting. The ohms setting will not work. The meter shown is a Fluke 16 (replaced now by the 116). The capacitance setting looks something like this: -I(- good luck

[@johnnyrotten52]

Great job. I was about to question your meter leads after the 2 start caps were both open. ha!

[@katherinerodgers5319]

Hi I am wondering how to lift a compressor out when your to short to reach it? a train unit .

[@Omastian]

Most helpful information. Thank you.

[@nicholasbantell2520]

Good video. I did not read through all the comments on this video but have you ever encountered a problem cap (electrolytic) having issues with equivalent series resistance failure which does not show up on a “standard” capacitance tester. I have seen this type of failure in electronics and was curious if the same issue can effect these motor start type capacitors.

[@gerrymcadams7517]

Great video, I have learned a lot from your videos. Question: If a 5-2-1 kit is installed and it fails. Will the unit still run? And can it damage the compressor by using a 5-2-1- compressor saver ? thank you for your knowledge. Waiting for next video.

[@grayfurnaceman]

gerry mcadams If the motor is a PSC motor, it will run if the run cap is ok. However, if the motor is a compressor on a TXV controlled refrigeration system, the pressures do not equalize in the off cycle, so the unit may not start with the lower starting torque of the run cap. The 5-2-1 should not damage the compressor but if it is not necessary to have a hard start kit, I would not install one. Hope this helps. GFM

[@gerrymcadams7517]

Thank you for responding, I installed a 5-2-1 kit because my in-rush reading was 10 amps over the LRA. It lowered my in-rush reading by 20 amps. I have a Scroll with a TXV it is 12 years old. It stared fine before and it sounds about the same after the kit. What do you think? Should i leave it in? Thanks again. Really enjoy your videos.

[@grayfurnaceman]

Well, we could argue forever on that one. Tell me more about the exploding cap. GFM

[@EddieLeverich]

I know of a company here in Louisville that gets $225 for a capacitor and they sell a few hundred a year at that price.

[@dpeagles]

I does seem the new caps don't last like the old ones. Perhaps the smaller size equals more heat.

[@rgallegos27]

Great video!! I tested a run capacitor that has 7.5 UF 370 V printed on it, I'm getting a reading of 6.8 is this still good? my blower motor wants to turn but it don't have enough power to turn on it's own... This all started when the brackets broke on the blower motor, I replaced the bracket and if I use something to turn the squeal cage it will only turn once then stop and motor turns very slow and hums...

[@EddieLeverich]

No amrad ever used by this company. All of them were genteq and diversitech. I can also tell you that the minimum repair was $200 for just about everything.

[@grayfurnaceman]

Your price is not too high, in fact it seems low. Ask them if Walmart delivers and diagnoses.

[@dpeagles]

Not to mention, if a service tech works a 10 hour day, he will be lucky to bill out 5 hours. Drive time, lunch time, time on the phone, time spent with paperwork, time waiting on the customer to get home.

[@jimbola77]

very nicely explained thanks good video!!!!

[@grayfurnaceman]

+jimbola77 Thanks for the support. GFM

[@grayfurnaceman]

Does it trip while running? GFM

[@survivormary1126]

Hi, I have one of those big old beasts that has 15 on one side and 20 on the other, but it has a resister on it. I am trying to use two together to replace it. I am wondering if you know if I have to put a resistor back on it or can I use the new ones without it? Thanks for a great video, now off to check out your others!

[@grayfurnaceman]

I would not install the resistor. GFM

[@KungFuMaintenance]

1:33 (~..~) That's me LoL. Good practice ~ Keeps you alive.

[@SidewaysInTraffic]

I understand it may cost a lot to run a business, but I was charged $107 for a 35/5 capacitor, and $85 for a 12.5 capacitor. Well long story short my AC is acting up again and I'm looking to do it myself this time after $609 bill for cleaning and capacitors 2 months ago. Moreover, seen those exact capacitors at HomeDepot from $5-15. How do you justify that markup?

[@quebraho]

Good job. uF or, rarely μF stands for micro farad and mF stands for millifarad. (12:38)

[@grayfurnaceman]

You have to take that up with Amrad. GFM

[@gerri577]

so my table top fan went dead. I have no electrical knowledge. so i looked at a DIY video and it said i can twist the capacitor to make contact and if that works, I can replace it. Is that safe?

[@grayfurnaceman]

I would be amazed if the fan had a capacitor. Most of this type motor is shades pole type. Could you send me a pic? GFM

[@LubaLuba1]

So all seems to work good except AC unit outside stays on after thermostat turns off. What could this be? I did not change contactor with switch yet. Could this be the problem?

[@grayfurnaceman]

Check the contactor to see if it is stuck closed. GFM

[@LubaLuba1]

not sure what is close position because I when I pushed it in still was on is there a way to test it??

[@steelcantuna]

Are you saying that the “hard start” kit is a second capacitor? So when you install a hard start kit you actually have another capacitor to help the original capacitor? I went outside to check the capacitor on my HVAC. I noticed there was already a hard start kit installed (years ago?). It looked like a capacitor to me so I checked it for capacitance. It read zero, so I thought it’s not a capacitor. I did an ohms reading & it came in at 10.89 Thanks

[@grayfurnaceman]

Michael Powell The start cap is a much larger capacitor than the run cap. It is only used to give the motor a hard start. If the cap has a resistor between the terminals, it would not show on the cap tester. GFM

[@joemcorbett]

Start cap is for starting. Run cap is for running. Start cap is only used during start up. The potential relay opens and drops the start cap out as soon as it isn't needed any more. The run cap acts as a line three, It charges and discharges in between line ones pulse and line twos pulse adding a more power pulses per second. Corbett Cooling on Face book if you have any other questions.

[@grayfurnaceman]

Thanks for the info. Did you know there are 4000 farad caps? GFM

[@toneblair]

I have a hard time wrapping my head around how they work, did you make the follow up video?

[@grayfurnaceman]

I have a number of them. Try this one kzbin.info/www/bejne/aoLFgYB9brBkY6c GFM

[@chessmith5043]

Enjoyed this video very much- you are a great teacher. Can you tell me how to identify the wires I need to switch if I want to reverse the rotation of a capacitor start motor? I understand they supply the start winding, but how are they identified on the terminal board. Thanks for your reply! Ches Smith Columbia, SC

[@grayfurnaceman]

ches smith Capacitor motors cannot be reversed in rotation unless they have terminals for reversing. All wires are on the diagram on the motor. It could be on the side, or under a the wiring cover. Actually, you could reverse the end bells but the wires will be on the shaft end. Hope this helps. GFM