Heating, Air Conditioning, Fridge, HVAC/HVAC


Hello. I have an old Trane HVAC unit on top of my house. During the summer it began intermittently switching from cool to heat while in cool mode. A technician looked at it and determined that the control board needs replaced and in the meantime he placed a CPS magnet over the solenoid. This was effective in preventing unit from switching to heat for the remainder of the summer. Now that it has cooled down and I wish to run the heater it seemed logical that if I simply removed the magnet from the solenoid and switched the thermostat to heat it would blow hot. However after removing the magnet the unit is not blowing hot when the thermostat is moved to heat. Additionally, when switching the thermostat back to cool it is again blowing hot intermittently. Can you provide any advice for next step? Thank you.

Since you are still having an issue with the heat and cool, I would guess the control board is ok, but the reversing valve needs to be replaced. (I am assuming you did not put the coil back on the valve stem).  The rev. valve has a slide that moves back and forth inside it.  You need that slide valve to work while heating in order to get the defrost cycle to work.  If the control board is still active, then it will have all sorts of issues if it does not control the valve and will never defrost.  The slide valve will provide heating or cooling regardless of the t-stat depending on which position it is in.  The t-stat just tells it which position it is suppose to be in.


Heating, Air Conditioning, Fridge, HVAC

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Craig HVAC Expert


I have been in the HVAC field for the past 18 years. I can help with most HVAC questions. I work on commerical buildings for the most part, and have yet to find anything I could not troubleshoot and repair, when repairable. I work on small 1 ton units to a 2500 ton chiller. Troubleshoot air flow, elect, and control problems. I attend regular classes to keep up with the latest and greatest.


I work on commerical sites, hospitals, gov't buildings. I can troubleshoot just about anything in the HVAC business.

5 years trade school, VFD training classes, Liebert factory training, some York and Trane factory training.

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