Fan turns on but compressor doesn't


Old 12-21-13, 03:40 PM
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Join Date: Dec 2013
Location: Australia
Posts: 2
Fan turns on but compressor doesn't

Hey, this is my first post on this forum after having searched around for a solution in previous threads but couldn't find anything matching the same circumstances as myself.

Basically, my house has a very old industrial ducted a/c unit and when we switch it on at the thermostat, the blower in the roof turns on but the compressor outside doesn't.

I opened up the electronics panel outside and found that when switched on, one of the three contacts turn on and there is a slight electrical humming, the rest don't turn on. The particular contact that turns on is labeled as the evaporator motor contactor.

I (bravely) pushed in the other contacts with an insulated screw driver and the compressor and fans turned on momentarily. I guess this could mean the control voltage is irregular but I'm just not too sure where to test on my multimeter to get a correct reading.

Also, the main logic board has been replaced twice over the past year or two so I'm a little skeptical to believe that this could be the problem. Weirdly, my father used to let water run on the unit and it would turn on, however, now it doesn't turn on with or without water flowing over it.

Any help would be appreciated! I've also taken a few pictures of the setup for more information.
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Old 12-21-13, 03:52 PM
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Welcome to the forums from down under

Most of us are predominantly familiar with the equipment that is used in the States here.

I'd need a better, bigger, brighter schematic to help you further or a link to one online.
I'm guessing APAC is the company. Is there a model number there.
Old 12-21-13, 06:46 PM
Thread Starter
Join Date: Dec 2013
Location: Australia
Posts: 2
Hey PJ, thanks for the welcome!

Yeah there is a model number, S26 HP/CHB, and the brand of the A/C is "Carrier" (APAC was a distributor of their A/Cs at the time I think).

The only problem is the unit is from 1997 and there seems to be nothing online when I search for it. I have an old photocopied document that my parents got when they bought the machine, though the model numbers on there don't match up to the unit we have (document talks about an S24 as opposed to an S26).

If you'd like I can scan the document and attach it if you think it'll help, though it doesn't contain any electrical schematics in it. I can also take a better picture of the circuit diagram I uploaded earlier if that'd help.

A new development has also occured, the condenser now turns on by itself as soon as you give it power from the main supply, whether the thermostat is turned on or not. I'm going to assume that the contactor has somehow shorted in the past two hours. The fans still don't turn on however.

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