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Catch14me · 04-08-2011, 04:53 PM

2003 Monaco with Duo-Therm roof heat pumps heats but does not cool on the rear unit. The front Unit works properly. The control appears to be OK Fan works, furnace. It seems to me that the Unit is just not reversing the cooling process or it wouldn't blow hot air when in both heat mode and cool mode. Any suggestions? How difficult is it to remove the AC circuit board? Thanks for help.

GaryKD · 04-08-2011, 06:00 PM

Hi Catch14me,
You're on the right track thinking the unit will not reverse to the A/C mode. However, it may not be the control board. There is a mechanical "switch" that does the reversing. It has been so long since I heard anyone complain about this I have forgotten the details. Before jumping into the control board, get a schematic and see if you can find the mechanical switch. I do not remember if the switch is replaceable or not. Sorry, I do not have the details, but this was a prevalent problem on units in your coaches age and older.

RV Wizard · 04-09-2011, 02:37 AM

Most times the reversing valve solenoid coil goes bad. Trouble shoot the circuit to verify.

Pogo · 04-11-2011, 05:59 PM

You could probably check the reversing valve solenoid when the unit is running, by sliding the solenoid off of the valve when it is energized for couple of seconds. Then put it back on. If the solenoid is good, you should hear a click and the refrigerant gas making a "swoosh" sound as the gas reverses direction.

Catch14me · 04-12-2011, 12:07 PM

Thank everyone for the comments and suggestions. I located the solenoid and removed it while the unit was running. No clicks or changes. I tapped gently on the device that the solenoid slide on to which I assume contains the valve. I have not determined if the solenoid is getting a signal from the circuit board to activate. The solenoid looks like it would not be too diffficult to replace if that is the problem. I also tried switching from cool to heat several times to see if that may help. The compressor is very warm and the tube connected to the aluminum coil is cold.The valve does not appear to be something that I can replace and is contained in a cylinder with numerous tubes connected. I guess the next step is to try get the wiring diagram and see if I can test the circuit that activates the solenoid. If unsuccessful take it to the shop unless there are other suggestions to try.

RV Wizard · 04-13-2011, 04:15 AM

If I remember correctly that solenoid is energized in the cooling mode with 120 vac. Check for 120 volts at the coil when in cool mode and compressor running. If you have 120 vac at coil but it does not change over (shift internally) the coil is probably bad. Ohm it out to be sure it is not shorted or open. Good luck.