AC compressor won't shut down

GASPEDDLER · 03-09-2013, 08:45 PM

I hope some of you HVAC guys can give me some advise. I'm camping out with the family for the week and after turning off my AC at the thermostat I notice the compressor was still humming/running. I had to turn the AC breaker off to get the compressor to shut down. It was cooling fine, too cold actually so I raised the temp setting on the thermostat to warm up my TT and that's when i notice the humming coming from the roof. It's a 15 k dometic with wall mounted thermo. Any advise would be appreciated.

Iggy · 03-09-2013, 08:54 PM

If what you say is rue then the 120 volt relay that the termostat controls has burnt conttacts that are made or on and won't release. As you said the only way to stop it is to shut down the ac breaker.
Time to get it into a shop and have them check it out.
Here is a picture of mine. The yellow is the 120 volts av power and inside the gray box is a relay that is controlled by the thermostat and turns on and off the compressor and fan.

fonzie · 03-09-2013, 09:10 PM

If you have a digital thermostat make sure it is set to auto so the circulating fan on the AC does operate only when required....

GASPEDDLER · 03-09-2013, 09:31 PM

So do I need to remove the box to access the relay or can I merely remove that plate at the upper right corner of the box?

Iggy · 03-09-2013, 09:42 PM

GASPEDDLER

First verify what Fonzie said.....
If you have a digital thermostat make sure it is set to auto so the circulating fan on the AC does operate only when required....

GASPEDDLER · 03-09-2013, 10:12 PM

No, not digital.

Iggy · 03-09-2013, 10:23 PM

It also may just be the termostat went bad and is always calling for cool.
You need to have someone do some testing and figure it out.
You will need more electrical troubleshooting with muiltimeter to do it.

VinceU · 03-09-2013, 10:29 PM

Quote:

Originally Posted by GASPEDDLER

So do I need to remove the box to access the relay or can I merely remove that plate at the upper right corner of the box?

Its only one screw, give it a try, your looking for a low voltage control wiring of a 110 volt switch (relay) It should be easy to ID with the yellow AC cable on the right. Use a meter when its open and see if the 110 is always going through, with thermo high and low positions. The schematic is too small from here but you can ID the relay by the connections and its the only4 wire device on it.

GASPEDDLER · 03-09-2013, 10:33 PM

Ill get someone to have a look at it on Monday, thanks for the replies guys.

GASPEDDLER · 03-09-2013, 10:49 PM

VinceU · 03-13-2013, 02:02 PM

How did you make out?

GASPEDDLER · 03-13-2013, 02:42 PM

About three hours after starting this thread I cranked on the AC to cool down the TT before we went to bed. I figured I'd run it in the "on" fan position setting for twenty minutes. The damn thing worked fine and has been working fine ever since. The temps have in the low 60's and highs in the 70's so there has been little need for me to run it much. Ill just wait until I get home and have my guy go through the system. It probably needs a good cleaning as well. Thanks for all your help guys. Stay warm!

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