My blower quite blowing,checked fuses,ok. put 12 volts to the blower,ok. So pulled the CCU and looking at it it looks fine. How do you check it out and see if it is good or bad? I have no power going to the blower so it must be the CCU but how do you tell if it is good or bad. thanks

jump the strip fuse to be sure its not fuse related. same problem, mine turned out to be poor contact at strip fuse (which was brand new)

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Paul
Benz-less
I need an SDL !

Did you pull the CCU apart and inspect the circuit board. If not try that. Make sure there aren't any burn or bad solder connections.

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I took the CCU apart and looked at the board.They all look good.I will jump across the fuse and see if that helps.

Jumper the fuse strip still no fan. I took the CCu all apart and I mean ALL. Is there anything else that will cause the fan to not run? If not will order up a rebuilt CCU tomorrow.

If it doesn't work on any setting including Defrost, then it has to be the CCU. If it ONLY works on Defrost then it could be the fan speed control box or the blower resistors.
You might try remelting ALL of the solder joints on the CCU circuit board before ordering a new one. It's really not that difficult since you already have it disassembled...

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'83 300D Turrrbo 295K miles

THANKS-Will try that and if that does not work will get a new CCU.

do you get ANY functions of CCU to work? IE, does a/c comp come on? If not, Id say the CCU is toast. But if A/C comp does work, and its just the fan not getting input, Id be tempted to figure out why (broken wire, ect..) before splurging the $400 for another CCU.

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Paul
Benz-less
I need an SDL !

You don't have what year model in your signature (hint).
That would help.

When my blower stopped a few weeks ago on my 300D,
and seemed to only work on Defrost, which bypasses everything
and gives 12V straight to the blower, I thought the replacement brushes
I had put in last year and 6,000 miles ago were bad.

Then I read that if there is a loss of vacuum to the CCU system the
blower wil not work. Irritating, but true.

Found a vacuum leak under my hood, fixed it, got my blower back.

Your results may vary.

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80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250

It is on a 1985 300sd.I could not get any of the push buttons to work. So I will look for a vacuum leak.But thinking it is the CCU.