Having problems with the CCU and blower fan. Works fine on defrost mode. In other modes it works intermittently. I put a meter on the leads to the fan and when it quits no voltage to fan, main air door closes, air recirc door closes and there is an audible click sound like from a relay or something. Basically it appears like the unit has completely shut down as if the stop button has been pushed. It will cycle on and off like this while in the a/c or e/c mode. In a/c mode though the compressor remains engaged even when the unit shuts down.

I've read through the archives but am unclear about where the various relays and switches are located. Thanks for the help!

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1983 300D 280,000
1983 300TD 125,000 Killed by oak tree.
1983 240D Sold
1986 Ford F250 Diesel 6.9l 169,000

It is quite possible the CCU has a few cold solders on the board. You'll have to pull it out to check.
This is a common failure.

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83 SD

84 CD

Forgot to mention that I have pulled it and resoldered every joint I could. That was a couple of years ago.

__________________
1983 300D 280,000
1983 300TD 125,000 Killed by oak tree.
1983 240D Sold
1986 Ford F250 Diesel 6.9l 169,000

Today I unplugged the aux.pump and grounded what I believe to be the blower fan temp switch, on the thermostat?. No change. Interesting though that when I unplugged the blower fan temp switch the fan still worked. I assume this switch simply grounds out when hot. Testing it when hot showed no path to ground. I did replace this switch a couple of years ago. Am I misunderstanding how this switch works?

__________________
1983 300D 280,000
1983 300TD 125,000 Killed by oak tree.
1983 240D Sold
1986 Ford F250 Diesel 6.9l 169,000