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Thread: Heat Pump Not Coming On

  1. #1
    DIY Junior Member DeweyBeach's Avatar
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    Default Heat Pump Not Coming On

    My Carrier heat pump is not coming on at all, although the air handler does move air. If I set the thermostat high enough, I get auxilliary (electric) heat, but the outside heat pump itself never activates. Similarly, if I set the system to cool and crank down the temp setting, the air handler starts blowing, but the heat pump doesn't operate. I've checked the fuses on the 240 volt line at the heat pump itself, and both have continuity, and no breakers are tripped at the breaker box.

    Any ideas on what the problem might be?

    Many thanks.

  2. #2
    Plumber jimbo's Avatar
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    Beyond checking the fuses and breakers, which you have done, HVAC repair is not usually a DIY project. You have control boards, contactors, the start capacitor, and the compressor itself. Not to mention all the t=stat wiring, etc.

  3. #3
    DIY Junior Member DeweyBeach's Avatar
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    Quote Originally Posted by jimbo View Post
    Beyond checking the fuses and breakers, which you have done, HVAC repair is not usually a DIY project. You have control boards, contactors, the start capacitor, and the compressor itself. Not to mention all the t=stat wiring, etc.
    Thank you -- I understand. I have no intention of opening my heat pump and I am at the point of calling a service tech for help. I was just curious to know if there was anything obvious I was overlooking. For instance, if there's a possibility the thermostat is to blame, I could easily swap that out.

  4. #4
    DIY Senior Member burleymike's Avatar
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    It is probably too cold outside for the heat pump so the electric (backup) heat is working. There is an outdoor thermostat that determines when it is too cold.

  5. #5
    DIY Junior Member DeweyBeach's Avatar
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    Thanks. Yeah, I'm aware that the heat pump won't work below a certain temp. However, the current outside temp is 60 and I just tried the system on heat -- at some point the air handler starts (as if it should be getting heat from the pump/exchanger and blowing it through the ducts) but the pump fan isn't turning on. If I push the thermostat up farther, the air handler keeps running and I get aux heat.

  6. #6
    DIY Senior Member burleymike's Avatar
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    If your system has high/low pressure cut outs look for a manual reset. If that is the problem you still have to figure out what caused the high or low pressure.

    Check that the contactor getting 24v from the thermostat. Make sure you have 240v at the line side of the contactor. If you are not comfortable with 240 VAC don't mess with it because it can burn/kill you real quick.

    Have a helper set the thermostat up above the ambient indoor temp and you listen to the contactor. If it has 24v and does not click that is your problem.

    If you are able to rule out the contactor the start cap might be bad. At that point you really need a tech to look at it.

  7. #7
    DIY Junior Member DeweyBeach's Avatar
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    Quote Originally Posted by burleymike View Post
    If your system has high/low pressure cut outs look for a manual reset. If that is the problem you still have to figure out what caused the high or low pressure.

    Check that the contactor getting 24v from the thermostat. Make sure you have 240v at the line side of the contactor. If you are not comfortable with 240 VAC don't mess with it because it can burn/kill you real quick.

    Have a helper set the thermostat up above the ambient indoor temp and you listen to the contactor. If it has 24v and does not click that is your problem.

    If you are able to rule out the contactor the start cap might be bad. At that point you really need a tech to look at it.
    Thank you so much!

  8. #8
    DIY Junior Member DeweyBeach's Avatar
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    Turns out the system had a leak, so the safety switch kicked in and prevented the heat pump from coming on...

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