Any HVAC people around? Need troubleshooting help

[MoneyPit]

Well my home a/c unit crapped out on me yesterday so I need a little help troubleshooting from an a/c guru.

The problem is that when I turn on the thermostat switch inside the house, the outside unit compressor/fan isn't kicking on. I busted out my trusty fluke meter and found that it's getting 120vac to the fan and compressor.... they just aren't coming on. I also read the motor leads and neither one appears to be grounded out. The breaker for the unit does not trip either.

Both the fan and compressor are wired to a dual round run capacitor, so I'm guessing that the capacitor is the culprit? I think it would be unlikely that both the fan and compressor would go bad at the same time. It is a Janitrol unit by the way. Any help would be appreciated cause my fauking house is burning up inside! LOL

Here's a capacitor similar to the one I have if it helps... thanks guys

 

[Worsedog]

Measure the voltage again. Unless that a/c is a serious antique it should use 220 to power the compressor and fan.


Also have someone in the house turn the termostat on and off to the a/c posistion. Listen to see if the relay in the condenser unit is kicking on and off.
It will be a very obvious "clunk". If there is a clunk check the contacts (with the circuit breaker off of course!!) of the relay for spiders or ants, they love to hide there.

If there is no clunk then the low voltage approx 24vac that controls the relay is absent or the relay coil or thermostat contacts are bad.


Hope this helps.

 

[MoneyPit]

The contactor works fine. The contacts close when the thermostat is turned on, which then sends the power through the run capacitor to the fan and compressor. I'll check out the relay too. From looking at the wiring diagram, I suppose it could also be the compressor motor overload engaging? Well, I will investigate further.

Thanks bro

 

[NIT2WN]

Make sure you're getting the full power through the contacts. I've seen ants get in there and stop the contacts from completely closing. Usually the fan or the compressor go out not both at the same time. You didn't have a lightning storm or powersurge did you? And your probably right about the capacitor but I hate to tell you yes and be wrong. They make a testor but I haven't had much to do with ac units in 17 years.

 

[SVT4ME]

To test your capacitor move your meter uf. Then read on the capacitor what the micorfarad it is. Place your black lead on the center post and then your red lead on the fan. What are you reading, is it what it should be?

 

[MoneyPit]

To test your capacitor move your meter uf. Then read on the capacitor what the micorfarad it is. Place your black lead on the center post and then your red lead on the fan. What are you reading, is it what it should be?

Would if I could man LOL

My fluke is older than dirt, and doesn't have a uf function, but I did read to ohms and the cap seems to be charging and discharging. I'm gonna bring it in to work tomorrow and test it there better. Thanks for all the help guys :beer: