Hello Steve300
Please make crystal clear, what area you soldered, someone may mistake the area and burn a board.

Attached Thumbnails

 

Hello Steve300
Please make crystal clear, what area you soldered, someone may mistake the area and burn a board.

Attached Thumbnails

 

Hmm, I'm not sure about Steve but I resoldered EVERYTHING in sight!!! The most common failure is at the pins, but I also did the main board and where the two side boards meet (probably second most common failure) the center boards. People take burning a board up a bit far.

__________________
Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

whunter:

Yes, I resoldered the area you circled with red ink (the solder side of the PC board).
I found 2 traces the solder were broken. This ACC unit PC board's design is very bad. It uses solder to connect 2 side PC boards to the main board. After close to 20 years of pushing on/off the buttons, those solder traces bound to break lose.

Well, at least it is repairable. You don't have to spend $200 to buy a rebuilt one.


Steve

I bought all new fuses as suggested, replaced the old ones, and nothing happened. It was a good starting point, though.

Finally today, after re-reading all the threads and misc. info on soldering the guts of the acc, I pulled the unit out to give it a try. Get this---my mother-in- law and I repaired it together, and it was no problem. Popped it back in when we were done, and all the buttons now do everything that they're supposed to.

Thanks to everybody for the advice and help. Another success story! If my mother-in-law and I can do it, anyone can!

__________________
1984 300TD Wagon--Astral Silver--Retired
1983 300TD Wagon--Dark Blue--Retired

Do you loan your mother in law out ?

I am impressed.
A triumph for DIY.

I have this same problem, and while I'm good with electronics, I'm a novice at mechanics. The ACC (Automatic Climate Control, I'm guessing), is that the thing behind the glove box? If it's what I think it is, my benz CD manual calls it an "electronic unit for blower speed control". The wiring diagram shows the push buttons being connected to it, and it's in turn connected to blower resistors and the blower motor.

Just to reiterate the problem, the blower comes on randomly. Sometimes (very rarely), it'll work perfectly, from when I start the car to when I stop it. Most of the time, it won't come on at all. Sometimes, it'll come on, then stop after a few minutes. Sometimes I'll leave the switch on, and it'll cut on a little while into the trip. When that happens, sometimes it continues working, sometimes it shuts off. I've been trying to find a common link between all the events, but so far, nothing. It seems to be independent of outside temperature, of engine temperature, of me messing with the buttons, etc. Although, about 50% of the time, if I keep pushing buttons at random, it'll come on after a while.

__________________
Gabriel
'91 350SD 162k
'83 300SD 210k - rear-ended and scrapped
'84 300SD 210k - totalled

I see the replies for blower trouble,
mine is fine.
Just no heat, ever, not even on defrost.
Can anyone help with that?
Thanks

The ACC, CCU, or whichever acronym you use is just a fancy name for the thing you are pushing the buttons on. It is right above the radio. The electric speed controller you're talking about generally doesn't go bad but it is in the engine compartment on the passenger fender (the thing with the coiled wires inside it). I bet your climate control unit just has a few bad solders in it.

Thevegmyster, I don't know how it could "never" have heat but if it has it only at slower speeds then goes away as you drive faster that'd be a bad monovalve. If it is parked in the sun a lot then perhaps the foam tube that brings the air down to the temperature sensor is bad and is pulling in warmer air than that in your car. I suppose it is possible that the temperature turn switch could be bad, but I've never really heard of this type of failure.
^Edit^ Does your auxillary water pump work? If not it may be getting in the way of the coolant trying to make it into the heater core to give you heat. If you have the ignition on but car not running do you hear the little motor running? Adding an inline fuse to its power wire would be a good idea, because a bad aux pump can lead to a bad CCU.

__________________
Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

Thanks, BoostnBenz,
There is never, ever any heat at all, even at freezing midnight.
You are right - there is no sound of the aux pump working!
AAAK! Now the bottom of the servo leaks at times.
I wonder if I ruined it...

Servo? the climate control leaks?! What is coming out of it? There is no fluid inside of it! Something must be going through it then. If something keeps leaking on it, it will ruin the unit eventually.

__________________
Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

This is a classic case of why you should put your car's year and model in your signature. If thevegmyster's car is a 1980 300SD, then it would have the climate control servo in the engine bay.

__________________
Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References

This is true....

__________________
Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

Sorry folks,
you are so right about posting model of car.
Thanks for your responses.



'80 300CD
non-turbo but GOES!!