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Only defrost/defog working on climate control

1K views 10 replies 4 participants last post by  w126Sam 
#1 · (Edited)
I figure it is probably a ccu problem, just wanted to make sure this isn't indicative of a more significant failure. The fuse for it just continuously blows. And if anyone has an automatic ccu for my US '84 500, lemme know what you need for it. Thanks guys.
 
#2 ·
Your Aux water pump has fried your CCU. Gen I aux water pumps are know to fry the CCU. But check your monvalve too. That would not cause the fues to blow though. Aux Water pump is undwer the Monovalve. replace it and wire in a fues to save later CCU's.
 
#3 ·
Possible, however, the default setting is defrost.

You may simply have a failing ACC unit.

You'll need to pull it, open it and examine the PC board.

By this time, many have succumbed to a "cold solder".

If you see a "volcanic" type of hair line crack around any solder point, re flow the solder, does that correct the issue?
 

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#4 ·
Yea I feel silly for not checking the circuit board from the get-go. Will do.

I'll have to look into the aux water pump and monovalve. Any telltale symptoms besides complete failure?

I had forgotten I was experiencing a few other symptoms before this happened. The heat only worked on high, and sometimes I needed to switch between settings to get it to kick in.
 
#10 ·
The newer thread describing a similar problem reminded me to update. CCU is fried, even the plastic casing had started to melt. So I'll be doing the aux water pump, monovalve, and ccu, being sure to add a fuse to the pump. Hopefully the pump isn't too much of a pain. I suppose it's time for coolant/antifreeze anyways.
 
#11 ·
Strangely, with the CCU out, I now have very low velocity hot air coming out of the vents. It's actually kind of perfect for fall. New parts are on their way, with a special thanks to 81126 for providing a good CCU for much less than he could have gotten.
 
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