This is my first post..But I'll try to be clear.

My 82 300 CD Turbo has been cooling just fine all summer here in Arizona.

However, now winter is here , yes even here in AZ. I set the heater for hot

air & it works just fine for about a half hr, goes to 120 Deg. I turn the

roller down a bit & the air goes full cold. I have reset the roller to hot a

couple of times & the warm air returns, but goes cold again.

The question of course is...Where's the fault? Control, Monovalve,?

Sensor,?

I've been following this forum for some time & I'm sure there are a good

number of you guys ,& Gals, who know this as just "Old stuff". This is

driving me nuts.. HELP!