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!!

So I took out the ACCU and resoldered the parts where the solder keeps the two board together. It worked great for the first three times I started the car after that, then I let it sit for a few hours, and went out again. This time it didn't work. I made 3 stops, and restarted my car 3 times, and it didn't work any of the times. On my way back home I remembered something about someone getting it to work by hitting the wood panel in front of the ACCU, and I did that, and the A/C came on.

Any ideas?

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

I too am having a major AC problem. We have a 1991 350SD with 80K. A few weeks agao, the AC was not blowing. Then, out of the clear blue sky, it started right up. Today, my Mother in Law started the car (I say she did it) and the AC was not blowing. I pulled the car apart, and checked the blower motor. It has power, and I bench tested it real quick, and it clicked over (did not do it long enough to make it turn. I then took apart the rest of the car...thinking it was the fan switches with a loose conenction...NOPE! My brother in law sent 12V to a pink wire that plugs in to the rear of the Temp Dial. The Blower motor clicked each time he touched the power..but never actually turned.

Can this be the Brushes everyone is taking about? I live in So Cal, and it has been really hot..the wife is not happy....Help...

the motor on bench.
You must run it up to speed.
Be sure the motor bushings are well lubed, and NOT sticking/binding = spins free by hand.







Have a great day.

__________________
ASE Master Mechanic
https://whunter.carrd.co/

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
2003 Volvo V70

https://www.boldegoist.com/

Ok...my blower motor spins freely, and the brushed seem to be good and making contact. When I say freely, it does not spin on its own, and needs asssitance, but it spins. I decided to put the blower motr back in and plug in the Blower Motor Regulator "porcupine". I turned on the AC and the blower motor was working fine..the air volume was low, but that is becasue everything was open...When I had the fan speed on Auto, the fan turned fast, on low, turned low (barley moved) and on high it turned fast.

Once the porcupine warmed up, the fan speed got slower and slower. Then finally the fan stopped turning...and the porcupine was super hot..could not even touch. My thought is the Blower Motor Regulator is bad? Help...any ideas, thoughts...anyway to test that or bypass it to test the fan?

There are 3 wires on the regulator-think pink wire, a thicker guage brown and a thicker guage green.

Help..need ideas..thoughts...Thanks...

Hope a member has a good used one for you.

Vehicle 1991 Mercedes Benz 350SD

Fastlane: Blower Regulator, Behr-Hella, Note: Sometimes Referred to as the "porcupine".
http://catalog.peachparts.com/item.wws?sku=W0133-1598146


Blower Motor Links Page
Blower Motor Links Page

Yea I used to hit it as well. I went through and resoldered everything, it fixed all the problems.

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

I was gonna resolder everything, but I don't see the point. I mean, I understand why the sides would need to be resoldered, because all the stress from 20 years of the buttons pushing that board would break the solder joints.
What I don't understand is why the regular solder joints would go bad, and more importantly, why hitting the ACCU would make it work. That second one especially boggles my mind.

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

Because internally one of the solders have broken free but don't always make contact. It sounds like you have the exact same problem I had, perhaps you may think it'd be pointless to resolder all of them but it fixed mine. I was told that over 50% of failed CCUs fail in the pins on the side of the CCU, the rest is normally where the buttons are soldered onto the boards and the others are where the side boards meet.

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

Just to wrap up the thread... I resoldered almost every pin on the ACCU and the A/C has worked great for 3 days now. I found a few cold solder joints on the boards, and I'm guessing that's what was the problem. Thanks everyone.

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