I am having some heater issues. Thinking its probably a CCU issue but wanted to see what you all think.

My heater has worked great since I have owned the car but last night when driving I turned the temp dial down and it turned to cold air and the blower continued to blow full speed. I then selected max heat and it wouldn't do anything but blow cold air. I selected defrost and it still blew nothing but cold air. I turned the CCU off and back on still the same. I turned it back off and waited a few minutes then on and it started blowing hot air again. Selected defrost and it was blowing hot air. It seems that when I have it on heat and then select the temp dial to a cooler temp it will only blow cold air till it has been turned off and sits for a period of time. Left the car not blowing heat when I parked it for the night. When I started it this morning turned the defrost on and it warmed up and blew hot but when I selected heat and later rolled the temp dial back a bit again cold air only and cold air again on defrost. Guessing I need to pull the CCU out and check the wiper for the temp dial and check the soldier joints but just wanted to check see if anyone had any other ideas.

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1982 300D

Also the vacuum controller. Look it over for cold solder joints.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Where is that vacuum controller located you are talking about? Did notice today that its not blowing full blown cold air its just not hot like normal when I have it on max heat or defrost.

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1982 300D

Subbed .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Thanx Mr. grumpy ! .

I looked for it but didn't see it .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

So I just did get to pulling out the ccu. Haven't gotten it apart yet but in the mean time I did notice that when I had it out I had to move the car over a little when I shut the car off I heard an air leak coming from the CCU area since it was pulled out. Just curious how to check those change over valves? Guessing I can put vacuum on them and check them but how to check the power side of things. Just put 12v to a terminal and see if lose vacuum or how do these valves actually work? Thanks for any input.

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1982 300D

Thanx for the update .

I've been too busy to rip into mine and now the blower fan has stopped working entirely so sooner or later I'll rip into the dashboard .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

As with most things, there is a procedure in the Factory Service Manual for checking the changeover valves. I encourage everyone to read the FSM before you even take things apart.