Inexpensive capacitor tester

[lincwelder225]

What do you guys recommend for an inexpensive testor to test a/c capacitors?

 

[Bert_]

Any old ohm meter will do the job most of the time.

Short capacitor terminals to discarge then connect meter set to ohms (high range). Meter should start out at or near zero, then slowly climb up to infinity (the speed will depend on the size of capacitor.

If the reading stays at zero or at a low value the capacitor is shorted or leaky.
If the reading is always infinity then the capacitor is open or possibly still has a charge (try reversing the leads)

This will not give you the exact value but will usually indicate a failure. It will be just as reliable as any cheap tester. If you want a real reliable tester it needs to test the capacitor with high voltage not the 9v or so that most use.

 

[willf650]

What do you guys recommend for an inexpensive testor to test a/c capacitors?

Most decent multi meters will test a capacitor. I have a bunch of different fluke meters and every one but an old 77 will read a capacitor. If you really need to read one I would just get a multimeter that reads capacitors.

You can probably get a cheap one that reads capacitors and not spend a ton. I also have a cheaper field piece meter that will also read caps.

 

[rlitman]

Any old ohm meter will do the job most of the time.

Short capacitor terminals to discarge then connect meter set to ohms (high range). Meter should start out at or near zero, then slowly climb up to infinity (the speed will depend on the size of capacitor.

If the reading stays at zero or at a low value the capacitor is shorted or leaky.
If the reading is always infinity then the capacitor is open or possibly still has a charge (try reversing the leads)

This will not give you the exact value but will usually indicate a failure. It will be just as reliable as any cheap tester. If you want a real reliable tester it needs to test the capacitor with high voltage not the 9v or so that most use.

An ohm meter is a good start to know if the cap is working or failed. A multimeter that reads capacitance will also tell you if it has a partial failure.

Metal bodied metallized mylar film AC caps will often bulge on the terminal end when they fail open BTW.

I have a capacitor ESR meter at work. That's a bit more sophisticated, and tests caps at a user selectable frequency. You don't need it to tell you if the cap is already dead, but I use it for predicting future failures.

I also have a megger. That is capable of testing components at higher voltages, but is NOT something most people need, or should be using.

 

[lincwelder225]

Any old ohm meter will do the job most of the time.

Short capacitor terminals to discarge then connect meter set to ohms (high range). Meter should start out at or near zero, then slowly climb up to infinity (the speed will depend on the size of capacitor.

If the reading stays at zero or at a low value the capacitor is shorted or leaky.
If the reading is always infinity then the capacitor is open or possibly still has a charge (try reversing the leads)

This will not give you the exact value but will usually indicate a failure. It will be just as reliable as any cheap tester. If you want a real reliable tester it needs to test the capacitor with high voltage not the 9v or so that most use.

Looking for one to check/ test an a/c capacitor. Thanks for the advice on using a regular ohm meter to check one, I'll have to try that on my old a/c capacitor that was weak.

 

[lincwelder225]

Most decent multi meters will test a capacitor. I have a bunch of different fluke meters and every one but an old 77 will read a capacitor. If you really need to read one I would just get a multimeter that reads capacitors.

You can probably get a cheap one that reads capacitors and not spend a ton. I also have a cheaper field piece meter that will also read caps.

I have a fluke 73 III... would that work or is it less advanced than the 77?

 

[lincwelder225]

An ohm meter is a good start to know if the cap is working or failed. A multimeter that reads capacitance will also tell you if it has a partial failure.

Metal bodied metallized mylar film AC caps will often bulge on the terminal end when they fail open BTW.

I have a capacitor ESR meter at work. That's a bit more sophisticated, and tests caps at a user selectable frequency. You don't need it to tell you if the cap is already dead, but I use it for predicting future failures.

I also have a megger. That is capable of testing components at higher voltages, but is NOT something most people need, or should be using.

I did know that they swelled up when bad... mine didn't and was "weak" . I need one that can read bad and " weak" or partially failed ones.

 

[James-W]

If you have an electronics repair shop near you, take the capacitor there and ask them if they will check it for you. If they have a Sencore capacitor checker like I did at work, they can use it to check the capacitor value, check for leakage, check for equivalent series resistance (ESR), and check for Dielectric absorption. The Sencore capacitor checker will tell you in no uncertain terms the condition of the capacitor.

 

[willf650]

I have a fluke 73 III... would that work or is it less advanced than the 77?

I just looked and it’s about the same as the 77 and it can’t read capacitors.

This one is in stock at my Home Depot and it reads capacitors.

https://www.homedepot.com/p/Commercial-Electric-Auto-Ranging-Digital-Multi-Meter-MS8301B/206177758


This one is only $20 on Amazon and reads capacitors.

https://www.amazon.com/dp/B01M7ZD1VN/?tag=atomicindus08-20


Sent from my iPad using Tapatalk

 

[gungatim]

I have a bunch of VOM's but none of them do capacitance, so I ordered this one off amazon a year ago to do capacitors.
https://www.amazon.com/gp/product/B00Y245JRE/?tag=atomicindus08-20

works great and only $15.

you can do some BASIC testing with the ohm meter, but if you have a marginal cap or unidentified caps and want to know the actual values, not just if they are shorted, but within spec, you need a VOM with Capacitance testing ability.

 

[zmaxmotorsports]

Depends on your idea of inexpensive.

 

[lincwelder225]

If you have an electronics repair shop near you, take the capacitor there and ask them if they will check it for you. If they have a Sencore capacitor checker like I did at work, they can use it to check the capacitor value, check for leakage, check for equivalent series resistance (ESR), and check for Dielectric absorption. The Sencore capacitor checker will tell you in no uncertain terms the condition of the capacitor.

Nothing like that around here... That would be a good idea though!

 

[lincwelder225]

I just looked and it’s about the same as the 77 and it can’t read capacitors.

This one is in stock at my Home Depot and it reads capacitors.

https://www.homedepot.com/p/Commercial-Electric-Auto-Ranging-Digital-Multi-Meter-MS8301B/206177758


This one is only $20 on Amazon and reads capacitors.

https://www.amazon.com/dp/B01M7ZD1VN/?tag=atomicindus08-20


Sent from my iPad using Tapatalk

I think I'll order the one from Amazon... Thanks for your help!

 

[lincwelder225]

I have a bunch of VOM's but none of them do capacitance, so I ordered this one off amazon a year ago to do capacitors.
https://www.amazon.com/gp/product/B00Y245JRE/?tag=atomicindus08-20

works great and only $15.

you can do some BASIC testing with the ohm meter, but if you have a marginal cap or unidentified caps and want to know the actual values, not just if they are shorted, but within spec, you need a VOM with Capacitance testing ability.

Thank you... Im going to try the one recommend earlier for $20... If i need another option, ill try the $15 one you recommended. Thanks again!

 

[bonneyman]

You can always test the cap "live". And you don't need a special tester.

This article give a good explanation.

https://www.achrnews.com/articles/135163-testing-the-run-capacitor-while-the-system-is-running

 

[LS6 Tommy]

Any old ohm meter will do the job most of the time.

Short capacitor terminals to discarge then connect meter set to ohms (high range). Meter should start out at or near zero, then slowly climb up to infinity (the speed will depend on the size of capacitor.

If the reading stays at zero or at a low value the capacitor is shorted or leaky.
If the reading is always infinity then the capacitor is open or possibly still has a charge (try reversing the leads)

This will not give you the exact value but will usually indicate a failure. It will be just as reliable as any cheap tester. If you want a real reliable tester it needs to test the capacitor with high voltage not the 9v or so that most use.

Just FYI, shorting a charged cap is a good way to kill it... It doesn't really matter anyway because shutting off the power to the unit and waiting 5 minutes will drain it down just fine.

Tommy

 

[Dragfluid]

To test it cheaply, just charge it up and toss it to a someone near by.

 

[AP514]

To test it cheaply, just charge it up and toss it to a someone near by.

LOL...reminded me of when I was in A & P school we used to charge up old Magnetos and toss then to other guys in the class