Very Old Lennox AC Unit Not Working


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Old 07-25-10, 09:03 PM
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Very Old Lennox AC Unit Not Working

I have a very, very old Lennox AC unit Model HS9-261-1P that isn't working. The outside motor won't spin and of course, no air. I did test and am getting power to the unit and the furnace fan blower is also working, so I'm guessing my problem is somewhere with the outside condenser unit.

So far, I've replaced:
1. Start/run capacitor (definitely bad)
2. Contacter (definitely bad)
3. Motor (not sure was bad but had an exact replacement available cheap, so figured it couldn't hurt)
4. Fuses

Compressor cap hasn't been tested, but looks good.

Any thoughts what could be wrong or I'm overlooking? (Just an average DIYer with limited capabilities).

The few repair places we've had out in the past usually want to replace the system rather than work on it. However, we rarely use the central air (5 or 6 times a year) and don't want to replace it until the furnace goes (also on its last legs). Help please. Thanks!
 
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Old 07-26-10, 02:22 AM
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You need to check for 24v control from the thermostat to the contactor and 220v at the contactor. If you're not sure how to do this it would be best to find someone that will work on it for you. 220 volts is nothing to mess with if you don't know what you're doing.
 
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Old 07-26-10, 08:09 PM
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Something New

Okay, so I went back out to my condenser and found that if I manually press my contacter switch (with a piece of wood), the motor and compresser come on and everything works. I am guessing that I am not getting power to activate the contacter. Yes? No? When I replaced the contacter, I reattached the wires exactly as I had taken them off, so why no power?.

Any thoughts now as to why it's not working and the contacter isn't being energized? Is there a relay or switch somewhere that could have gone bad, perhaps on the furnace itself? There doesn't appear to be any such thing in the actual outdoor unit. Thanks.
 
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Old 07-26-10, 08:17 PM
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Originally Posted by mmichaelk
Okay, so I went back out to my condenser and found that if I manually press my contacter switch (with a piece of wood), the motor and compresser come on and everything works. I am guessing that I am not getting power to activate the contacter. Yes? No? When I replaced the contacter, I reattached the wires exactly as I had taken them off, so why no power?.

Any thoughts now as to why it's not working and the contacter isn't being energized? Is there a relay or switch somewhere that could have gone bad, perhaps on the furnace itself? There doesn't appear to be any such thing in the actual outdoor unit. Thanks.
You're not getting 24 volt control voltage to the contactor. Could be the thermostat, a low pressure cutoff switch, a condensate overflow safety switch, a bad 24 volt transformer, a broken or loose wire in the control wiring, a fuse in the 24 volt control circuit, etc, etc, etc.
 
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Old 07-27-10, 07:19 AM
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Troubleshoot the 24-V control circuit in a systematic manner with a voltmeter.
 
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Old 07-28-10, 02:04 AM
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So far, I've replaced:
1. Start/run capacitor (definitely bad)
2. Contacter (definitely bad)
3. Motor (not sure was bad but had an exact replacement available cheap, so figured it couldn't hurt)
4. Fuses

Compressor cap hasn't been tested, but looks good.

Any thoughts what could be wrong or I'm overlooking? (Just an average DIYer with limited capabilities).
The money you spent on replacing good parts most likely could have payed for a service call and diagnostics.

If you don't understand how to troubleshoot basic electrical circuits with a multi-meter, get the system checked out.
 
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Old 08-02-10, 05:11 PM
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no need to be mean here the guy is trying to learn and from the balance of my checkbook i can tell (20 year old in college) that learning AINT CHEAP. Get your multimeter ready and report back for specific instructions mm
 
 

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