AC Fan runs, compressor does not turn on

[JW84345]

The original Armstrong AC on my 69 Overlander stopped working last summer. The fan runs, but the compressor does not kick in. From what I gather on the forum, there could be a transformer or capacitor problem.

Can any knowledgable contributor give me a better understanding what to look for and where? How do I test?

Heading to the outerbanks in a couple weeks and would love to get the old air going

[meadowlm]

Do you have a schematic for the Air Conditioning unit? I have one for my 72 Armstrong and can send it to you if you need it.
Check the wiring going to the compressor. If there is 110/120 going to the compressor then check the capacitor/start relay or the over load. If there is 110/120 going to your compressor and through the overload and the start circuit is ok, your compressor is shot.
If no voltage going to the compressor, there are two places to look. Check the relay to pull in the compressor and check the thermostat to make sure it is sending a signal to the relay.

[JW84345]

Thanks for the input. I do not have a schematic and appreciate the help.

[Gael79]

Hello,
Best of luck. I have a 1970 Sovereign with similar problems. On mine, the compressor is either cycling, or just straining, and then cutting out. Pulled the capacitor out today, will check it at work tomorrow. I will post any results. Maybe it will help you with your unit.

Good luck with yours!

[overlander63]

Originally Posted by Gael79

Hello,
Best of luck. I have a 1970 Sovereign with similar problems. On mine, the compressor is either cycling, or just straining, and then cutting out. Pulled the capacitor out today, will check it at work tomorrow. I will post any results. Maybe it will help you with your unit.

Good luck with yours!

Yours may be the condenser fan not running properly. Ours did this on our Sovereign, it would blow cold air, then not so cold air, then kind of luke warm air, the compressor would start laboring from high head pressure and shut down. It turned out the condenser fan had stopped working. If you can, crawl on the roof with the a/c running, and watch the fan blade up there. If it starts, then slowly stops, or doesn't come on at all, that's the problem.

[JW84345]

Thanks. I would be interested to know what you find.
My compressor does nothing. No sound, no click, no hum, etc. If I can get home earlier enough tomorrow, I'll pull the shroud and check for voltages as meodowlm outlined. Hopefully it is something simple -- and replaceable in the next week or so. Otherwise .. I'll pack fans and leave the windows wide open catching the ocean breeze (instead of the "bay breeze").

[Gael79]

Thanks Terry, I'll look into the condenser fan issue.

The capacitor for the squirrel cage fan,condenser fan, and compressor run circuit is an "all in one unit, left hand side, just behind the compressor ( big oval brick, you can't miss it). It checks out O.K. for me, but JW84345, you may want to check yours.

There are 3 wires going in to the compressor, on top, on mine. One of the HVAC guys at work told me that if there are 3 wires, they shoud be a common, a hot run wire and a hot start wire. That means that there is a start capacitor that I have not found yet. Yours almost sounds like a "no power at the compressor issue. If I were you, and you are able, I believe I would verify that you have power at the compressor. If no power then look at your contactor (relay) If power, then overload switch, etc.

Again best of luck. If I stand inside of my trailer, and look into the rear vent, there is a data plate that tells me the model number and manufacturer. Check yours if you get a chance, and let me know if it is a TR21-12. (That is what mine is) Maybe we can talk each other through this...

Best of luck,

[Gael79]

Oh, one more quick note. Many A/C systems today have low pressure switches that will disable the compressor, should a low freon condition exhist. While crawling around on mine yesterday, I traced the coolant lines pretty well, and did not see such a switch. I had a couple of people tell me that that could be an issue for me, but if no switch is present, low freon should not keep the compressor from running, unless all the oil has drained out, and the compressor is seized. Prior to looking for this switch, I was almost convinced by one guy that this was the problem with my unit.

Just a bit of useless information... low freon would make it blow hot, but the compressor should still turn,

[JW84345]

All,

Thanks for the input. Turns out the problem was with the thermostat. I was mistaking the partial movement from the left side to open a circuit with the proper functioning of swinging all the way over to the right to make the connection there to turn the compressor on. Once I realized it, it was so obvious I can't understand how I missed it when I looked at it last year.

Bottom line is it now works great. I had actually rigged a home window unit to fit in the back bathroom window. We ended up leaving that unit and rigging home.

Actually have not need much air here on the outer banks. It has been cool with a breeze. Air did come in handy last night as we had to close the trailer up due to some really heavy storms.

Jim