Heat Pump Not Turning On

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  #1  
Old 12-30-07, 02:13 PM
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Unhappy Heat Pump Not Turning On

Hello, I have a problem with Heat Pump Unit, it is a Nordyne 12 Seer unit. Unit will not turn on in Heat or A/C. Contactor will click but not pull in. Replaced Contactor thinking coil might have been bad. The inside unit works ok (Emerg. Heat) and fan will blow when HP is supposed to be running.

I do not get 24V to the contactor but I have 24V at T-stat and outside where wires go to Defrost control board. I can manually activate contactor and unit will run. Pipe warms up as it is supplying heat but unit will not start.

I am fairly competent electrically and it seems that something (safety) is holding out my control voltage.

Any help would be appreciated!!!

Thanks alot,
Tom
 
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Old 12-30-07, 06:53 PM
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Hi Tom,

May want to check at the air handler and see if you got 24 volts at Y and C. If you do, then follow the wire out to make sure the wire hasn't been damaged.

If all looks good, see if you have a low or high pressure switch.
 
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Old 12-30-07, 07:40 PM
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Thanks for the reply. I am getting 24V from the handler out to the board on the Heat Pump. It is just not letting it go to contactor. This is why I figured something was telling it to stay off. I will check for low or high pressure switch. I will post results back!!

Again Thanks alot,

Tom
 
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Old 12-30-07, 07:54 PM
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Ok, yeah look for the pressure switch, and see if that is keeping it off.
 
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Old 12-30-07, 11:56 PM
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Thanks for the reply Jay. My thing is this, If I look on the wiring schematics it shows no low or high pressure switch anywhere. Surely, it has to have something to protect the unit if there is a pressure issue. What would I need to look for? I know it would be somewhere along the pipes and assume it would have a wire(s) going back to the Defrost control board to prevent the control voltage from pulling in contactor.
I am no HVAC person but learning alot from reading other peoples problems and possible solutions.

Hopefully I find it soon, temp is going to start dropping and not excited about running E heat 24 hours a day.

Thanks,
Tom
 
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Old 12-31-07, 04:59 AM
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What is the full model # of the unit? I"ll see if I can find something..

Look for something on the pipes with wire on it. It most likely is between the defrost board and contact switch.

If you can't find anything chances are may have a bad defrost board.
 
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Old 12-31-07, 06:52 AM
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The model number on the heat pump unit is T3QC-024K. I had thought about the defrost control board as well but I did not want to start changing multiple parts without knowing what the problem was.

I will search for the pressure switch today.

Thanks,
Tom
 
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Old 12-31-07, 07:58 AM
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Here is what I found at the Heat Pump:

Wires going to motor.
Wires going to reversing valve.
Wires going to thermostat mounted at coil.

No reset button or any switches inline with pipes.

I rechecked the voltage going to defrost board and I have 27VAC at the board. Again, I get the contactor clicking as it sounds like its trying to pull in but I do not get the 24V at the contactor to pull it in.

Sounds more like it may be the board. Any thoughts???

Thank you,
Tom
 
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Old 12-31-07, 11:47 AM
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Yeah, it seems like you don't have any pressure switches...

I would OHM out the thermostat on the coil to see if it's open or closed.

Otherwise, I am with you, it's the defrost control.
 
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Old 12-31-07, 03:37 PM
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Ya Jay, I ohmed the t-stat and it is showing open which I would presume to be right. I think when it reaches its temp then it should close.

I got a board that should be here Wednesday, should have ordered it Friday but was not sure if I needed it.

Does this sound right on the NO/NC state of the t-stat?

Appreciate all the help, glad I came across this site. Hopefully I can help others with some of their problems.

Thanks,
Tom
 
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Old 01-01-08, 05:31 PM
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Yeah, if there is no frost on the coil, then should be open..

I just wanted to make sure it was open, and not stuck closed.
Enjoy the New Year!
 
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Old 01-02-08, 04:05 PM
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Talking

Everything is working great now!!!!!!!!!!!!!!

The problem was the defrost control board. Although the board itself did not have any physical burn spots there was a hidden problem in it somewhere.

After further investigating the possibilities I noticed that on the board schematics it showed a Low pressure and high pressure switch that was jumpered from 1 connector to the other connector so that eliminated that from keeping the unit from coming on (unless it was on the board).

For anyone having a problem with a Nordyne heat pump unit, my trials may help you. Here is a recap of my troubleshooting:

Check to see if you have 24V coming from thermostat to outside unit defrost board then check that you can manually make the contactor and the unit runs. I did not have 24V at contactor.

I replaced contactor anyway, only $9 so no big deal.

The defrost board ( part# ICM DFORB-AB1004 ) is probably the culprit. I got my from a local appliance store for $75 (also available on Ebay if you are not in a hurry for one). The Nordyne part# 621301A , 621579-C , 621579B and 917178 should be the numbers compatible with the one I purchased which was a ICM302-C.

Apparently this board controls all the control voltage to this unit.

I have learned about heat pumps by working on my own and hope someone can find this useful.

Thanks Jay for your help, this forum is great!!!
 
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Old 01-02-08, 04:28 PM
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Glad to hear you are up and running!

Glad to be here and help you out, and thanks for the update!
 
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