Compressor starts and immediately shuts off.


  #1  
Old 06-21-10, 05:31 PM
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Compressor starts and immediately shuts off.

This is a very old system, york CL48-6B, was running great until one night I realized the system was just blowing warm air, and the outside unit was not running. When you flip the t-stat switch to cool, the fan and compressor come on for all of a second, and shut down. After 30 seconds or so it will try again, sometimes it will run for 20 seconds then shut off. Then eventually all it does is click every once in awhile. Took the access panel off to see if there was anything obvious, all connections look good, there is one 3 wire cap that is not burnt or bulged, but could not test as multimeter is at work. Where should I start? Thanks!
 
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Old 06-21-10, 06:10 PM
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so both the compressor and fan shutdown at the same time. maybe its tripping somekind of overload that resets after a while.
 
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Old 06-21-10, 06:24 PM
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yes both are at the same time, which is maybe 5 seconds after the relay clicks
 
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Old 06-21-10, 07:50 PM
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could be a faulty contactor switch. does the inside unit work correctly throughout this.
 
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Old 06-22-10, 05:16 AM
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Yes air handler is blowing throughout this all.
 
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Old 06-22-10, 09:08 PM
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then it sounds like a bad contractor. do you know how to take electrical readings and use a multy meter. you want 24 volts at the contractor. you want to be careful though as some wires carry 240 volts.

http://diyhvacrepair.com/RepairScripts/contactor.php
 
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Old 06-24-10, 08:08 AM
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I want to tack onto this thread. I have an older Lennox system (built in the 90's, unsure of the model at the moment) and noticed the air was blowing warm. Checked the thermostat and it was still on "cooling" mode and you could hear the whining in the outside unit that usually precedes the compressor kicking on. The air handler in our basement is still working fine. I turned the heat pump off to prevent any further damage. This was Tuesday night. Last night, I turned the heat pump back on and it did a similar thing to what you're saying: the compressor kicked on for a few seconds then kicked back off.

I actually listened to the unit as it ran and it was not running smoothly (you could hear the heat pump "struggling" rather then running at a smooth, constant RPM). At the moment, getting that dreaded "you unit is completely dead" prognosis would be pretty crippling financially so I'm really trying to get to the root of this problem. Any ideas? Could a bad contactor do this? I know a car's compressor won't run if the freon is out; could it be something as simple as it doesn't have enough freon to engage or is that simply not how residential heat pumps work?
 
 

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