ACC Unit Repair - PeachParts Mercedes-Benz Forum

tobybul · #1 05-29-2007, 12:29 PM

I resoldered the connection on the ACC unit but that di not seem to help. I tried accessing the reverse side of the board where all the electronics are to test the resistors or whatever's there but cannot figure out how to get to the flip side.

Any thoughts please?

funola · #2 05-29-2007, 01:15 PM

Can you post a pic? I have not worked on the ACC but I just successfully repaired a Tach amp and may be able to offer some advice.

toomany MBZ · #3 05-29-2007, 02:19 PM

I have done the same thing, with the same results, on my late '82 300. I pulled a unit out of a 190, and looking at it, there are some tabs, clips on the bottom side, good luck.

tobybul · #4 07-23-2007, 10:37 AM

much to my chagrin, I still have not gotten my ccu to work.. or is it the ccu thats bad? the thing is my fan rarely turns on... not even on the defrost mode. I do get natural ventilation as long as I'm moving and I believe my compressor actually kicks in when it calls for cooling. Heat also works properly. But fan rarely comes on. Any ideas?

rrgrassi · #5 07-23-2007, 10:50 AM

How is the fan itself? Brushes in good shape?

tobybul · #6 07-23-2007, 10:55 AM

Quote:

Originally Posted by rrgrassi

How is the fan itself? Brushes in good shape?

Last fall, I replaced one of the brushes on this fan. I ground down a large brush so it fits the slot. The fan had been working more often b4 I messed with the ccu but still not as it should have. As posted above, I resoldered the ccu terminals. And now, rarely works....

I guess I am wondering if I should look somewhere else besides the CCU. Maybe open up the fan again and chk the brushes? Is it worth trying another CCU? (I actually tried another CCU with the same results). Are there other components I should be checking?

Jeremy5848 · #7 07-23-2007, 12:04 PM

First, unplug the fan and try running it directly from 12 Volts. That will tell you whether it's the fan or not. Then check all of the other connectors and grounds including the box of fan resistors on the passenger side inner fender. If all that is OK, it has to be a CCU problem.

tobybul · #8 07-23-2007, 12:37 PM

Quote:

Originally Posted by Jeremy5848

First, unplug the fan and try running it directly from 12 Volts. That will tell you whether it's the fan or not. Then check all of the other connectors and grounds including the box of fan resistors on the passenger side inner fender. If all that is OK, it has to be a CCU problem.

Good idea... I'll be doing that in the next couple of days....I haven't seen resistors where you described but i'll look....btw, who is a good source for small brushes. I might replace them while its out of the car. I heard Radio Shack may carry them that can be easily adapted to the fan's brush holder. I got the previous one from NAPA but they where a too big and needed a bit of grinding down.

Update: Just remembered... its vacuum cleaner shops that have an assortment of electric brushes. I don't think Fastlane carries them..

funola · #9 07-23-2007, 01:00 PM

I've found Sears Hardware has a good selection of carbon
brushes.

Quote:

Originally Posted by tobybul

Good idea... I'll be doing that in the next couple of days....I haven't seen resistors where you described but i'll look....btw, who is a good source for small brushes. I might replace them while its out of the car. I heard Radio Shack may carry them that can be easily adapted to the fan's brush holder. I got the previous one from NAPA but they where a too big and needed a bit of grinding down.

Update: Just remembered... its vacuum cleaner shops that have an assortment of electric brushes. I don't think Fastlane carries them..

Jeremy5848 · #10 07-23-2007, 02:56 PM

The resistor box in my '85 looks like this...(picture). It is an unlikely failure point but you might as well check it anyway, especially to make sure the plug is clean and in its socket solidly.

My fan motor's commutator (the part the brushes contact) was so worn down at 212000 miles that I replaced the entire motor, $85 from one of the on-line sources.

Jeremy

tobybul · #11 07-26-2007, 09:38 AM

I removed and checked the blower motor last night, tested it and worked fine. I believe my ccu is fine since the acc unit behind the glove box responds when I operate the ccu.

The blower works now. I think its because I spun it a few times while connected to the fan terminals in the car but b4 I put it back in the housing. B4 this, I noticed it tries to start but it could be that the armature is a bit worn and carbonized and not getting enough contact.

So far, the blower responds accordingly and the CCU works as it should. I drove to work this AM with the AC on with no problems.

I suspect though that the blower motor may be due for a replacement just from wear on the armature.

tobybul · #12 08-01-2007, 10:38 AM

after running it for several days, my ac system is now working fine and would like to share the work I did. Symptom was fan was coming ON very intermittently at any setting. From the start:

1. thought my ccu was bad (which it probably was but can't say for sure) so I resoldered all connections on the ccu board. No change.
2. took out blower, changed brushes, cleaned cumutator. No change
3. replaced blower (with newer used unit). Voila!!!! Works consistently now.

The problem apprarently was that the cumutator was quite worn..

Fuzzball · #13 08-22-2007, 01:00 AM

The motor in my wifes 84 300D just quit working the other day while we were driving down the road. The compressor is still engaging and as was stated earlier, I get cold air flow (very faint) when I have it engaged and I'm cruising at good speeds.

I haven't done anything yet, but from the looks of this, I need to start looking at my blower motor.

Anyone think it could be anything else? The ACC unit seems fine. One minute I was freezing, the next I got a blast of heat in my face and the blower quit blowin...

tobybul · #14 08-22-2007, 10:10 AM

Quote:

Originally Posted by Fuzzball

The motor in my wifes 84 300D just quit working the other day while we were driving down the road. The compressor is still engaging and as was stated earlier, I get cold air flow (very faint) when I have it engaged and I'm cruising at good speeds.

I haven't done anything yet, but from the looks of this, I need to start looking at my blower motor.

Anyone think it could be anything else? The ACC unit seems fine. One minute I was freezing, the next I got a blast of heat in my face and the blower quit blowin...

Had same symptoms as yours... my compressor was kicking in and got airflow only when cruisiing....blower worked intermittently... changed it and now works.