Outside condenser unit won't shut off


  #1  
Old 09-13-02, 10:58 AM
Ed R.
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Outside condenser unit won't shut off

I have a heating/cooling system with central air. The outside unit runs continously(both compressor & fan) regardless of how the thermostat inside is set. The heat/off/cool switch can be set to heat or off & the outside unit still runs. It doesn't matter where the thermostat temperature is set, the outside unit still runs. Even when the on off switch on the furnace is turned off the outside unit still runs. The only way to stop the outside unit running is to turn off its breaker.

I have to keep the furnace fan switch turned on all the time or the lines and coil ice up. It is cooling just fine, just won't shut off.

I know its probably some interconnect stuck in the run position. What is the problem here and is there anything I can check or do myself without calling a technician?

Thanks, Ed
 
  #2  
Old 09-13-02, 12:22 PM
P
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Ed; there is a 2-wire low-voltage cable from the house to the out-door compressor that energizes a contactor coil in the compressor , switching 240 volts to the motor-circuits. Starting at the compressor, trace this cable back to the point where it connects to the interior control wiring. Dis-connect 1 of the wires from the connection point in an attempt to open the circuit and shut Off the compressor. If the compressor shuts Off then connect a voltmeter across the 2 INTERIOR connection points where the 2-wire cable connects to the inside wring. If you read 24 volts with everything "Off" then you will have to check the control wiring, starting at the thermostat. First remove the wire from the "Y" thermostat terminal, and then the wire from the "R" thermostat terminal if you still have 24 volts on the connection points.----Good Luck!!!
 
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Old 09-13-02, 12:30 PM
Ed Imeduc's Avatar
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Re: Outside condenser unit won't shut off

Originally posted by Ed R.
I have a heating/cooling system with central air. The outside unit runs continously(both compressor & fan) regardless of how the thermostat inside is set. The heat/off/cool switch can be set to heat or off & the outside unit still runs. It doesn't matter where the thermostat temperature is set, the outside unit still runs. Even when the on off switch on the furnace is turned off the outside unit still runs. The only way to stop the outside unit running is to turn off its breaker.

I have to keep the furnace fan switch turned on all the time or the lines and coil ice up. It is cooling just fine, just won't shut off.

I know its probably some interconnect stuck in the run position. What is the problem here and is there anything I can check or do myself without calling a technician?

Thanks, Ed
Check out the wire on the t-stat all the way to the out door unit do you have a short in it????? Then look and see if the relay on the condenser is stuck on??? Pull one of the low voltage wires off the relay and see if it opens.Just had a bug in the relay that had it held on, so look for that also,ants love to get in relays and burn up the points so they stay on or or or
wont come on also. Dont for get when you do this the unit is hot with electricity if you didnt pull the switch on it. ED
 
  #4  
Old 09-14-02, 09:45 AM
Jacque Schidt
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sounds to me like your contactor is welded closed. Unless this is a heat pump, a short in the low voltage would not bring on your cooling. (no 24V present to short to) So, a short or bad tstat wire would result in no outdoor operation.

A new contactor is something a reasonably competent DIY can do. Make sure the power is OFF! 240V present and can kill you.

A replacement contactor should cost about $20 if you can get someone to sell you one. I've seen them on Ebay. Installed by a professional, expect about $125.
 
 

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