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 Lennox compressor not working
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sweaty

3 Posts

Posted - 03/18/2011 :  11:07:14 PM  Show Profile  Reply with Quote
turned off ac several months ago, it was working fine then. Turned AC on today and its not working right. Lennox Mdl HS18-411-8P , fan on inside unit is running, fan on outside unit is running, every few minutes compressor will come on for a few seconds and stop, no strange noises. Gauge set is attached, with compressor not running low side is at 100, high side about 110, when compressor does engage low side pressure starts dropping, high starts to climb, compressor only runs about 3 seconds and stops again. I've checked contacts on mag contactor and wire connections. Any suggestions????????? Its friggin HOT!

Cozy.Support

5851 Posts

Posted - 03/19/2011 :  08:50:00 AM  Show Profile  Reply with Quote
Make sure that you do not have low voltage at the compressor due to poor connections in the wiring, Then check the run capacitor and make sure it is not shorted or open. This is best done with a meter that can test capacitors. Also, this unit has a start relay and start capacitor as well. Make sure the start relay is opening. The easiest way to do this is place a clamp on amp meter (if you have one) on one of the start capacitor wires and see if the current drops when the compressor starts. This model didn't have a low pressure switch when it left the factory so the starting components would be the most likely cause... worst case is compressor issues.



CozyParts.com, Inc. is an Independent Lennox Dealer providing a national parts distribution resource for Lennox parts since 2002. The Cozy.Support team does not provide a diagnosis for users of this forum. We do, however, try to provide information that will help servicers arrive at their own diagnosis.

Once you know what part you need, you can contact the Cozy parts department by using the link below
http://www.cozyparts.com/Lennox-Parts/locator_form.aspx
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sweaty

3 Posts

Posted - 03/19/2011 :  2:30:51 PM  Show Profile  Reply with Quote
checked voltage at mag contactor , with compressor not running voltage was 245, when compressor kicked in voltage dropped to 220. Unit has a metal case capacitor, looks factory, and a hard start capacitor (wires go to main capacitor terminals) that looks like an add-on. Not sure where start relay is, only see main capacitor, hard start capacitor, mag contactor, and some type of pressure switch with a reset button (overcharged system once and it popped this reset, drained a bit, hit reset and it worked again, that was 2 years ago). I'm pulling capacitors to clean terminals, may try a new hard start capacitor, since I think thats only part I can find on a Saturday.
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sweaty

3 Posts

Posted - 03/19/2011 :  2:33:43 PM  Show Profile  Reply with Quote
Just looked at unit again, hard start cap is labeled "Relay and Hard Start Capacitor".
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Cozy.Support

5851 Posts

Posted - 03/19/2011 :  4:47:35 PM  Show Profile  Reply with Quote
quote:
Originally posted by sweaty

Just looked at unit again, hard start cap is labeled "Relay and Hard Start Capacitor".


"Relay and Hard Start Capacitor" is an aftermarket device that did not come on the unit from the factory. Most likely the factory start relay and start capacitor were removed.




CozyParts.com, Inc. is an Independent Lennox Dealer providing a national parts distribution resource for Lennox parts since 2002. The Cozy.Support team does not provide a diagnosis for users of this forum. We do, however, try to provide information that will help servicers arrive at their own diagnosis.

Once you know what part you need, you can contact the Cozy parts department by using the link below
http://www.cozyparts.com/Lennox-Parts/locator_form.aspx
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