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In-Wall A/C Compressor Won't Turn Off #27329
07/10/03 07:43 PM
07/10/03 07:43 PM
T
ThinkGood  Offline OP
Member
Joined: Aug 2002
Posts: 1,081
Milwaukee, WI
I have a through-the-wall air conditioner, 220V, digital settings.

It started misbehaving when I tried to turn it off (by pressing the big red ON/OFF button).

The compressor still runs even though the display indicates that the unit is off.

I pulled the plug immediately--naturally, that shut the compressor. I left the unit unplugged for a few hours and tried again with the same results.

Any ideas as to what is wrong with the thing?

From the little I know about this stuff, if that compressor runs and the rest of the unit doesn't, the compressor will burn out...

Work Gear for Electricians and the Trades
Re: In-Wall A/C Compressor Won't Turn Off #27330
07/10/03 08:31 PM
07/10/03 08:31 PM
Trumpy  Offline

Member
Joined: Jul 2002
Posts: 8,231
SI,New Zealand
Just at a guess, mate,
I'd say that the Compressor contactor has welded closed, this happens a bit.
Hope this helps. [Linked Image]

Re: In-Wall A/C Compressor Won't Turn Off #27331
07/10/03 08:35 PM
07/10/03 08:35 PM
T
ThinkGood  Offline OP
Member
Joined: Aug 2002
Posts: 1,081
Milwaukee, WI
Ouch...

Re: In-Wall A/C Compressor Won't Turn Off #27332
07/10/03 08:36 PM
07/10/03 08:36 PM
N
NJwirenut  Offline
Member
Joined: Sep 2001
Posts: 806
Bergen County, NJ
Definitely sounds like the control device for the compressor has failed in the ON position.

Usually, these are fairly large mechanical relays, subject to the usual contact welding problems, but I have seen one unit which used solid state relays, in which the output device (SCRs or TRIAC) failed by short-circuiting.

Either way, it sounds like you will need to change a relay.

Re: In-Wall A/C Compressor Won't Turn Off #27333
07/10/03 09:17 PM
07/10/03 09:17 PM
T
ThinkGood  Offline OP
Member
Joined: Aug 2002
Posts: 1,081
Milwaukee, WI
The unit was here when we bought the house...there is a second 220V unit that was here (both of these are Carrier brand, no more than 5 years old) that stopped cooling about 2 years ago.

I guess it's time for some more fans [Linked Image]

Re: In-Wall A/C Compressor Won't Turn Off #27334
07/11/03 05:21 AM
07/11/03 05:21 AM
Trumpy  Offline

Member
Joined: Jul 2002
Posts: 8,231
SI,New Zealand
ThinkGood,
I work quite often with the Carrier brand of Air Con equipment, if you need a hand fault-finding the unit, let us know! [Linked Image].
The company I work for over here, is a Service Agent for these units and I've fixed HEAPS of them.
That larger unit, you mentioned, sounds like it's lost it's gas (Refrigerant), my guess is there will be a small leak in the system (which is easily repaired!), the main cost would be in re-charging the system.
But, sometimes it can just be cheaper and easier to replace the units, if they are getting on in years.

[This message has been edited by Trumpy (edited 07-11-2003).]

Re: In-Wall A/C Compressor Won't Turn Off #27335
07/11/03 06:36 PM
07/11/03 06:36 PM
T
ThinkGood  Offline OP
Member
Joined: Aug 2002
Posts: 1,081
Milwaukee, WI
Could this component be the culprit?

OMRON
G4A-1A
24 VDC
20A 250VA

Re: In-Wall A/C Compressor Won't Turn Off #27336
07/11/03 07:34 PM
07/11/03 07:34 PM
Trumpy  Offline

Member
Joined: Jul 2002
Posts: 8,231
SI,New Zealand
More than likely, mate.
You could try disconnecting it from the unit and bench-testing it, with a 24V PSU.
The contactor should open and close as normal and this can be confirmed by hooking it up to an ohm-meter while applying the 24V to the coil.
If the meter reads a dead short with the supply ON and OFF, the contactor is shot.
I probably shouldn't have to say this, but mark the wiring sequence of the contactor BEFORE you remove the wires, Compressors don't take too kindly to reverse polarity!.
Hope this helps, I would imagine you'd be wanting to get the Air Con running again, I saw on the BBC weather report, last
night that temperatures are certainly getting up there in the US!. [Linked Image]

[This message has been edited by Trumpy (edited 07-11-2003).]

Re: In-Wall A/C Compressor Won't Turn Off #27337
07/11/03 08:05 PM
07/11/03 08:05 PM
N
NJwirenut  Offline
Member
Joined: Sep 2001
Posts: 806
Bergen County, NJ
That definitely sounds like it. Have replaced a lot of those nasty little things in A/Cs and microwaves. Contact welding is the usual failure mode, often evidenced by melting of the plastic case around one or both of the contact terminals.

There should be no continuity between the 2 top terminals unless there is power applied to the coil. If an ohmmeter check shows welded contacts, you can buy a new one for about $6 from Mouser Electronics:
http://www.mouser.com/catalog/613/580.pdf

Your relay is down at the bottom of the page.

Re: In-Wall A/C Compressor Won't Turn Off #27338
07/11/03 09:22 PM
07/11/03 09:22 PM
Trumpy  Offline

Member
Joined: Jul 2002
Posts: 8,231
SI,New Zealand
Gidday there Bob,
Since parallel importing started over here, in 2000, I've seen heaps of Contactors and CB's with Brand-names of reputable manufacturers on them, only to turn them over and find something like "Made in Pakistan" on them.
This is just not right!, it's blatant commercial plagiarism and judging by the number of faulty and just plain rubbish products,I've had to replace since then, a real blot on the good name(built up over years) of these manufacturers. [Linked Image]

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