Heat Pump Turning On Intermittently

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Old 06-19-19, 09:22 PM
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Heat Pump Turning On Intermittently

I've got a Nordyne heat pump that works very sporadically and intermittently. The compressor and fan will not consistently turn on when calling for cooling. It will work for a few hours here and there and then stop working for up to a day no matter how many times I try to turn it on and off.

The heat pump is getting 240v just fine. When it's not working, I noticed I'm not getting 24v to the r+y and r+o at the thermostat and I'm not getting 24v to the defrost board and contactor at the heat pump either. I tried replacing the defrost board but no luck.

I'm wondering if the control board in the air handler could be the culprit? Any other suggestions are welcome. This has been going on for the past 2 weeks and I really just want to get this figured out. Thanks in advance.
 
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Old 06-20-19, 02:12 AM
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Welcome to the forums.

It doesn't sound like any control boards are bad to me.
The 24v enters the thermostat on R and is switched out to Y and O. You need to make sure you have the system 24vAC first. There should always be 24vAC between R and C.

You didn't say where your air handler is located but if it's in an area where if it leaked it could cause damage..... you probably have a safety float system. That would be set up to kill the system if the condensate was overflowing the primary drain pan.
 
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Old 06-20-19, 07:26 AM
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The air handler is in the attic and the drain pan is dry, no water.

Where do I measure the r+c?
 
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Old 06-20-19, 01:16 PM
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That's the overflow drain pan. If there was a switch on the primary line..... it would shut the system down before water came out and into the overflow pan.

Look at the drain line near the unit. Typically it's 3/4" white PVC. Do you see a device anywhere in that line with two wires ?

You can measure the 24vAC at the unit and at the thermostat. If you pull the thermostat off the base..... the terminals are labeled. At the air handler.... it could be screw terminals or wire leads.
 
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Old 06-21-19, 05:06 AM
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Hi, I would check for 24 VAC @ the air handler first R to C both running and not , intermittent problems are tuff.
Will it work in the heat mode consistently?
Geo
 
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Old 06-22-19, 09:08 PM
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There aren't any wires coming out of the pvc drain. I am getting 24v to R+C both running and not.

Also, I noticed I'm only getting 1v to R+Y when thermostat is off. I believe this is supposed to be 24v? What does this mean?
 

Last edited by dsmboost; 06-22-19 at 09:33 PM.
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Old 06-24-19, 07:54 PM
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What thermostat do you have?

Does it use batteries?

If it uses batteries, are the terminals corroded and green?

Have you tried connecting R to G,Y and O ( using a wire nut) at the stat when this issue occurs to prove it isn't the thermostat?
 
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