Capacitor question

[anthonyk]

Do NOT change the capacitance.

Back in electrical engineering school we used to have that joke about smoke too! A good one!

anthony

 

[kenmac]

This past summer we had several 104 deg days . I replaced several capacitors on a/c units . Never replaced that many capacitors b-4 as I did durning those high temp. days

 

[JerryG]

Glad it was helpful.
Does anyone know how to build a tester for capacitors? The shop that I use to rebuild electric motors has a home made tester that uses a light bulb to check them. If they are good, the light bulb lights up. They are always so busy that I hate to bother them with how it works. I have so many electric motors it would be nice to be able to test the capacitors myself.

Jerry G: Thanks for the link.

I was in the same situation with the capacitor on my $88 Home Depot 3 year old tile saw that went bad. I took it out of the circuit and then used a stick to help push start the saw blade every time I started it. The tile saw ran fine once the blade got up to speed. Your link solved my problem for under $10 including shipping. In about a week or so, my saw should be like new.

 

[tallyho8]

Glad it was helpful.
Does anyone know how to build a tester for capacitors? The shop that I use to rebuild electric motors has a home made tester that uses a light bulb to check them. If they are good, the light bulb lights up. They are always so busy that I hate to bother them with how it works. I have so many electric motors it would be nice to be able to test the capacitors myself.

I just test capacitors with my $2 Harbor Freight meter. I put it on ohms and touch the wires to the 2 terminals and the needle goes up and comes back down. Reverse the wires and it should do the same thing. If the needle doesn't move or stays up, the capacitor is bad.

 

[Soundguy]

That's not their only failure mode though. Just because you see them charging off meter votlage doesn't mean they are at their correct capacitance.. etc.

soundguy

 

[kenmac]

I just test capacitors with my $2 Harbor Freight meter. I put it on ohms and touch the wires to the 2 terminals and the needle goes up and comes back down. Reverse the wires and it should do the same thing. If the needle doesn't move or stays up, the capacitor is bad.

Being in the A/C business for years, We have always tested our capacitors with volt /ohm meters. The meter puts a small charge to the cap. & then it discharges .

 

[Rara Avis]

Here's a visual for you...
Testing a capacitor

 

[tallyho8]

That's not their only failure mode though. Just because you see them charging off meter votlage doesn't mean they are at their correct capacitance.. etc. soundguy

Not saying that you are wrong, but after 38 years servicing air conditioners, I have never found a capacitor that was defective and checked out ok with this test.

 

[JerryG]

Do you need to discharge the capacitor first?

I just test capacitors with my $2 Harbor Freight meter. I put it on ohms and touch the wires to the 2 terminals and the needle goes up and comes back down. Reverse the wires and it should do the same thing. If the needle doesn't move or stays up, the capacitor is bad.

 

[tallyho8]

Do you need to discharge the capacitor first?

YES!!!