I "think" what the above post is referring to as the ballast resistor is what I would call the starting capacitor. The failure description is correct, but they can fail without expanding the case. If a motor, fan, or compressor, is hung up, there should be an overload relay/fuses/etc, that shuts it down. A control transformer will hum, and if that's the case, at least that end of the controls should be working. But the controls at the outside unit could be separate from the controls at the air handler and the stat. No signal, no start.



I don't know what the weather is where you're at, but last time for me it was 95, and my better half didn't want to hear anything but cold air flowing. Be careful and good luck.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

I'm going to call someone and learn what I can while they're here.

The temperature hasn't been too bad lately. I have a lot of trees for shade.


Lawrenceville, GA

Your correct.  I was getting the ballast resistor on my distributor confused with capacitor on the AC unit.

I have over 43 years in the HVAC field with WAY too many years doing service work.If the outside[condensing unit]is humming then it is getting low voltage[usually 24 volts].It sounds to me like either you are not getting power[220 Volts],check fuses/breaker,the unit needs a charge[has a leak somewhere]and the pressure switch is not letting the unit run,or the low voltage contactor[has two small wires that power the coil that brings in the contact points,and usually a number of larger wires] may be frozen or burned out,or a bug or bugs got in there and got fried stopping the flow of power to the compressor and fan.If the compressor was bad the fan should still run,if the fan is bad the compressor will run for a short time until the pressure switch kills it.If you have a low freon charge,DO NOT let the service tech just top it off,he[BY FEDERAL LAW] needs to find and repair the leak,Freon does NOT go bad unless you had a compressor internal burnout!! I hope this gives you some help in figuring out your problem!!! ROY.

52Mercury,292,5-Speed

Charlie,



I am a refrigeration mechanic, when you say the outside unit is humming? Fist thing to check is when you turn on the AC is the condenser fan running? If it is not, that is your problem (the compressor will go off on high head). This is caused by a bad fan motor or bad capacitor. If the fan is running and the compressor is just humming, this could mean that the unit has lost it's charge and possibly seized the compressor. ( usually if this happens though the breaker will trip). You can check a couple of things yourself, first as stated in the previous post, check your voltage going to the contactor. You should have a solid 208 or 230 V. If not, as stated, check wiring breaker panel and all connections. If this is good, if your meter has a capacitor checker, check to make sure the capacitor is reading the correct microfarads. ( the correct reading will be on the side of the cap and you should read within +/- 10%) If all this is OK, you can check the charge simply with your hands, the suction line going to the compressor (should be insulated) should be "beer can cold". The liquid line leaving the condenser coil should be fairly warm about 90 to 100 degrees. If not, this means your unit has either totally lost its charge or the compressor is not pumping. If the suction line is frosting up, then you have a leak and have lost a partial charge. As stated before, DO NOT allow them to top it up, they must find the leak, pump the system down, repair it and recharge the system.

I love the smell of burning rubber in the morning!

Ha, it was a bug smashed between the contacts of a relay.


Lawrenceville, GA

That was going to be the next thing I was going to suggest checking for

So you really needed an Entomologist, not a HVAC mechanic?

Frank/Rebop

Bristol, In ( by Elkhart) 

Charlie, Glad you found the " BUG " in your system.

For anyone else with an A/C home system problem a more common failure is a start capasitor. Mine was a 330 volt 145-174 MFD capacitor that failed. This gives the voltage kick to start the AC fan motor running and once it is running , then the compressor will start. A $ 20 dollar part from Grainger. Read about it on google and watch some Youtube videos AND MAKE SURE TO DISCHARGE the old capasitor before touching it. Pete

I used to carry some diazinon crystals or some kind of insect repellent , when I would find the tiny bugs in the contactor on service calls, I'd leave some in the control box. Get familiar with the drain line and fittings coming from the evaporator coil, flush these out every season, save yourself some trouble.





thanks, Mark