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HVAC Guru
HVAC Guru, HVAC TECH
Category: HVAC
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Experience:  15yrs in the HVAC industry with certificates and degrees.
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Outside hvac system will not stay running. I replaced the

Customer Question

Outside hvac system will not stay running. I replaced the capacitor...it ran about 4 to 6 hours and shut off. However the ac fan AND the furnace exhaust fan continue to run. (Exhaust fan does not run when the outside unit is working). I replaced the panel board...it ran a few hours and shut off again. (Exact same problem as before) I replaced the contactor....it ran a few hours and shut off again
Submitted: 11 months ago.
Category: HVAC
Expert:  HVAC Guru replied 11 months ago.

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Answer:

It sounds like the compressor is overheating and shutting down on thermal protection. Have you checked the current draw on the unit or seen if it is shutting off on a thermal limit or a pressure limit? If the condenser is dirty the head pressure could get to high and shut the compressor down.

All I ask is please use the Star Rating Link at the top of your page before leaving, that is the only way I am paid anything through the site and that will also get you a DIRECT LINK emailed to you to get back to me!.....tips are greatly appreciated so thank you very much for using this service. If you have any other questions just post back to me here anytime!

Customer: replied 11 months ago.
I had a tech come by, and he said everything checked out perfect. Of course the unit was running at the time. One other note, after having the breaker turned off all night, the unit started working when it flipped the breaker back on....oh my goodness, I just heard the unit kick back on!
Customer: replied 11 months ago.
now it's off again!
Expert:  HVAC Guru replied 11 months ago.

Check the wiring to the compressor you may have a bad wire to the compressor making a bad connection

Customer: replied 11 months ago.
All wires see to be fine
Expert:  HVAC Guru replied 11 months ago.

Can you check for power to the compressor with a volt meter to see if it has power when it shuts off?

Customer: replied 11 months ago.
Voltage is good at the breaker, at the pull-out switch beside unit outside, and at the contactor. I can manually engage the contactor and the unit comes on. So where does the signal come from that activates the contactor?
Customer: replied 11 months ago.
Voltage from the transformer is at 25
Expert:  HVAC Guru replied 11 months ago.

The signal comes from the board in the furnace or airhandler

Customer: replied 11 months ago.
Could this board be bad? I just put it on. Is something causing it go bad?
Expert:  HVAC Guru replied 11 months ago.

The board could be bad and not signalling the contactor, just double check for any condensate pump if you have one as a float switch could cause that issue as well as any pressure switch on the outside unit itself if tripped.

Customer: replied 11 months ago.
Hi,
I used a jumper wire from the post where transformer low voltage (x) enters the board to the red wire that goes to the thermostat. The system immediately started working. Will it be ok to leave this jumper in place until i can get a new board? Of course this is a new board that may have already been bad or either something is causing it to go bad. The fuse looks good on the board.
Expert:  HVAC Guru replied 11 months ago.

Yes you can do that until you can get it.

All I ask is please use the Star Rating Link at the top of your page before leaving, that is the only way I am paid anything through the site and that will also get you a DIRECT LINK emailed to you to get back to me!.....tips are greatly appreciated so thank you very much for using this service. If you have any other questions just post back to me here anytime!

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