Heatpump no Heat

I have a Weatherking 4 Ton Heatpump R410A. The unit cooled all summer with no problems. Now that cool weather is here I turned the heat on but no heat.The compressor will run about a minute then turn off. To get it to start again you must jump the test pins on the defrost board then it starts only to shut down again. I tried cooling again and it seems to be cooling with no problems. I did notice on the defrost board flashing LEDs the code reads low pressure control open. Any one ever have this problem. Or know what this could be.


Thanks !

 

A lack of airflow across the outdoor coil (usually caused by a dirty outdoor coil) or low refrigerant charge would be the most likely causes.

Does the outdoor fan motor run in heat mode?

 

Thanks Houston

No nothing outside runs unless your in cool mode. Im just wondering why it cools no codes. However go to heat and its a different story. Can I safely jump the low pressure control without killing it ?

Thanks again

 

I thought you saw the compressor run for about 1 minute in heat mode?

Bypassing a pressure switch would probably damage the compressor.

I would remove power to the outdoor unit and indoor unit for over 30 seconds and give it a heating demand to see if the outdoor fan runs with the compressor to help isolate the cause of this low pressure switch trip.

 

Thanks Houston
Yes I did say it will run in heat mode for about a minute. This is after everything has been reset and codes cleared. I have tried to wait it out powered everything down for several minutes. I also disconnected the wires to the low pressure switch and tried to run the unit. Results were nothing works not even defrost test.I have tried to run it again and everything is the same so hopefully I didnt hurt anything. I ordered another defrost board. Ill try that. Code is telling me there is a problem with low pressure but it checks OK so the next thing I guess would be the defrost board. Im not getting many answers to what the problem my be so ill just wonder off trying things.


Thanks again Houston !

 

It is unlikely that your defrost control board is at fault.

Lack of airflow across the evaporator coil and lack of refrigerant cause low pressure switch trips.

The outdoor coil is the evaporator coil in heat mode.

 

Ok, well how reliable are the LED codes that are shown through the defrost board. Code says the low pressure control is open but my ohm meter says its closed.

Thanks for your help Houston

 

Are you measuring as it drops out or after it has already locked out?

Operating pressure will be much lower than equalized pressure on the suction line.

Temporarily bypass the pressure switch and reset power to test.

Running a compressor with a lack of refrigerant is like running your car engine with no oil. This is only a short test.

 

Thanks again Houston

Ill check the pressure switch again today.
I was out there the other day and ran the unit on heat. Something I have never heard before came from the unit. It sounded like a loud very loud clanking noise. Clank clank clank clank on and on. I could not tell where it was from.
The temp outside was cold as I remember it was around 36 to 40. Anyhow everything was the same old same.
The next day I went out and it was 62 and I thought I would take the opportunity to check out a few things with it warm.
Anyhow I ran the unit on cool . It ran like a Rolls no noise at all. I had 43.1 degree tem out my floor regs. I checked subcooling temp high side line read 64 guage read 57, 7 degrees subcooling.
should be between 9 and 12 for this heatpump. Anyhow it being so quite I decided to try heat again. It dint make anything close to as much noise. And the temp of the low side line would burn to the touch best i could tell it was 95 degrees.

 

Sorry Houston I ran out of room .

Anyhow to continue It ran just fine for a minute then just shut down. But now the fan on the unit does run without the compressor. A call for heat and the fan comes on but no compressor. If i jump the test pins it gies to heating but then shuts down.

Thanks again

 

If the unit operates in the cool mode and not the heat mode it may be the reversing valve not moving to its full position to reverse the rolls of the condenser and evaporator. This condition will take out the compressor as it will over heat .

 

If it is a reversing valve problem I recommend having the unit professionally service since this site does not allow instructions on checking the refrigerant charge. (kinda sounds like it is not getting checked correctly but I will not get into this)

 

There is lots of information on reversing valves on the net .

 

I have ran into two faulty heat pump refrigerant metering devices (txv) in the last two weeks on RUUD/weather king 13pjl units. It caused the valve to stay closed the low pressure switch to open and equalize pressure very slowly. What is your model and serial number?

 

Ksefan

You hit it on the money.I had my AC guy come out and he noted the Expansion valve frosting up in heat mode. He replaced it and good to go now.I want to thank everyone who took time to try and help with this.

Thabks again guys !