Dometic A/C reversing valve/ relay board issue

[cruisecontrol49]

I have a Dometic A/C with heat pump that blows hot air in the cool mode.

I checked the wire at the reversing valve with a (tic tracer inductive type) voltage tester. There was no power in either heat or cool mode. I am assuming that the valve defaults to the heat mode when no power is present.

The refrigerant line going down into the cabin evaporator is warm and the line going to the condensing unit behind the fan up top is cool...(tells me there is nothing wrong with the compressor)

I replaced the relay board in the junction box (underneath the filter grill) 2 years ago. I noticed the relay terminal where the power feed comes into the relay board shows signs of overheating. The insulation on the wire is distorted and the plastic relay show signs of hot spots.

I am assuming that the reversing valve is fed by 110v from the relay board. I disconnected the harness feeding the rooftop and switched the stat to cool mode. The yellow wire that feeds the reversing valve shows no signs of voltage with a regular voltmeter. I checked the reversing valve coil for continuity and it reads approximately 450 ohms.

It appears to me that the relay board is bad again.

1) Is it ok to test this thing like this or do you need the bulb tester that the manual calls for?
2) Does it sound like the board is bad to you guys?
3) The unit is in a 98 Alpenlite and looks original...do you think it is worth another $75 board or just replace the whole unit?
4) Is the reversing valve 110v?
5)Anything you think I am missing or should check?

here are the specs;

1998 Alpenlite
Duo-Therm w/heat pump & analog stat
Model #59146.621

thanks for your time and your knowledge!

Bruce

[cruisecontrol49]

FWIW... my problem was a bad thermostat.

[cruisecontrol49]

Thanks for replying Doug,

I got a no power indication at the reversing valve coil.

I checked the relay feeding the reversing valve at the inside control board. I got a no power indication at that point.

I put a jumper,(from a known good 110v power source on the compressor relay) over to the load side of the reversing valve relay to feed the reversing valve. The reversing valve clicked when energized, so I powered the unit up and and it cooled normally.

I assume at this point that the relay controlling the reversing valve is bad. The fix would be a new control board as I see it at this point.

thanks for your time, help and knowledge,

Bruce

[dougrainer]

Yes, the default on YOUR year model is heat when the valve fails. Newer 12 button Dometic the default is COOL. You CANNOT use a voltmeter to check current going to the reversing solenoid. You use a 40 watt light bulb holder with 6 inch pigtails to test for 120 volts. You either have a reversing coil bad or the Reversing valve bad. There is no way to test for a reversing valve other than replacing the coil and then if that does not fix it the valve is bad and Dometic does not supply that part. YES, you need the Bulb tester I mentioned above. Doug