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A/c cooling fine but not heating

I think the control board or reversing valve in the outdoor unit is cactus as works in cooling mode but when switched to heating defrost led comes on indoor but seems to stay in cooling mode but fan dosent come on

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  • thetim May 11, 2010

    the fan outside? If the unit goes into defrost what happens is teh reversing valve switches to a/c mode out door fav stops and the refregant flow changes. after a set time defrost is over reversing valve switches you hear a swoosh freon direction changes again and fan comes on.



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The fan generally does not come on until the unit has achieved some high head pressure so that it can produce hot air. If it is low on gas it will not get to this stage.

Posted on Jul 02, 2009


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I have a Friedrich Ptac unit Model PDH15K5SE-A. The unit turns on ok but does not heat. Need advice what to do. Thanks

Does the unit cool ok? If yes, you likely have a problem with reversing valve. If no, likely a refrigerant problem.

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Sounds to me like the outdoor unit is malfunctioning. Could be a control board going crazy, could be the reversing valve leaking. A trouble call to the local contractor is the best idea, preferably a firm that deals with your brand.

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Coils freezing due to dust blocked coils and or air filter or short of gas. Service your unit completely.Please do not change any spare/s without knowing exact problem. Please follow the steps given below.

Toget proper heat, keep your temp setting at 30+ degree and also mode in "heat"position. If still no heat, check your heating sensor for closed circuit by anOHMs metre.It it's with RV, check power to RV.If it's with heatingelement check power to element. If power is there but still no heat meanselement defective. Replace new heating element. Thanks. To get proper cool, keep the tips as follows:
1. Check air filter is cleaned. 2. Check indoor coil is cleaned. 3. Checkindoor blower motor is working. 4. Keep in cool mode. 5. Set temp minimum 3degrees less than room temp.6.Check compressor is working with correctpressure.
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1 Answer

Haier Heat Pump System. Reversing switch is staying energized. hr30d2vae hb3600vd2m20-t

Hi, on all heat pumps, the reversing valve will be energized in the cooling mode only. The only units that the coil on the valve is energized in the heating mode is a Rheem and Ruud unit, they will default to cooling if they fail, this is crazy but they do it. You say your reversing valve is energized and stays there. I know you don't have a Rheem. If it is energized at the coil, it must be in the cooling mode. If you want it in the heating mode, and it is not switching the sleeve and ball bearing in the valve, it may be the thermostat, a faulty reversing valve 24 volt coil, or the control board at the outdoor unit it self. I wish I knew what season you are in, if you live where it is hot or where its cold right now? For a temp. fix on this, you can de-energize the valve by removing the panel where the compressor is and unplug the coil to the valve and it will switch back the other way if the valve isn't hung up its self. Very easy to unplug this coil, just grasp the black plug if you are sure it is energized, and pull it off of the 2- terminals to remove power to it. Depending on what mode it is in, I am assuming cooling as it is energized in cooling, you can also go to the circuit board and find the o or b terminal, which ever is being used to switch the valve, and take off the wire. This should kill the power to the coil. To find out which part is causing it not to de-energize, you will have to start at the thermostat after you hook all up like it was, and remove the o/orange wire or b/blue wire to see if it kills this coil. If so, the stat is bad. If not, wire it back up and go to the control board. Kill all power to the a/c. You want to take a look at the back side of this board. It is very tight and will have 4-stand off screws to remove. If you need to remove any wires, write the colors and terminals they come off of so you know where they go. This is very important. You just want to peak in behind it to see if you see any hot or burnt spots anywhere. I have seen this over, and over again. If so, this board is the problem. If you are still getting 24 volts to this coil when you are not in the cooling mode, you still have a faulty stat or control board. These are what sends voltage to the reversing valve coil.I would start with the stat as this is the least expensive of the two parts. If you don't feel you can tackle this, don't feel bad as this is something that you must be or have some training in to troubleshoot it. If this coil is energized, unplug it to kill the power to reverse it, so you can temp. fix this. Please keep me posted on this and please rate me as I know you will be kind. I will be checking in with you to see if you called out any one, and I hope that the reversing valve has not froze up on you.
A/C, Heating,

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1 Answer

Gold Star mini split heat pump 24,000 btu. Changed indooe as we as outdoor boards and still goes in cooling mode only. Reset button on outdoor board calls in heat but not by inside hand set. Len Cabana...

On a heat pump the difference from heat to cool is the reversing valve.
In cooling or heating the Y1 terminal will always be energized, this is the contactor.
Depending on brand the reversing valve will either be energized in Heat or Cool. At the outdoor unit check to see if the reversing valve is getting 24 volts in cool, if not check to see if it is getting 24 volts in heating. The easiest way to check if the reversing valve is shifting, is to feel the big copper tube, (it is not the suction line on a heat pump) this is a refrigerant vapor line. It will be cold in cooling and hot in heating.
Check your thermostat installation instructions and heat pump installation instructions to determine the proper terminal designations for your heat pump and thermostat. There are some brands out there that use the B terminal as common to the 24 volt circuit, so you have to check the wiring and make sure this is not common.
If it is energized in Cool then the Y1 and O terminal will be energized. You will have 24 volts from common usually the C terminal to Y1 and O.
If it’s energized in Heat then the Y1 and B terminal should be energized. You will have 24 volts from common usually the C terminal to Y1 and B.
If you get heat when you’re calling for cooling or vice versa then switch the wire between the B and O terminals.

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1 Answer

Hi, I have a wall mount midea split a/c model- MSG-36HR that will only heat. when put in cool mode it only blow's room temp air and the outdoor unit won't run. On heat mode it works normally. I have cycled...

Most heat pumps are 'fail-safe to heat'. That is: the normal position of the valve which reverses the function is in the position which provides heat. The reversing valve must be powered to switch to the cooling position.

Although the lack of valve function could be a mechanically defective reversing valve - it's more likely to be an electrical issue. Start with checking for power at the reversing valve's coil. If it's powered unpower it - you will be able to hear the reversing valve distinctively

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3 Answers

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Or the Yellow wire from the thermostat going to the unit that wont work in thecooling mode is broken,burned,or loose

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1 Answer

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