acc troubles still...... - PeachParts Mercedes-Benz Forum

lutzTD · #1 11-23-2006, 11:49 AM

can someone point me to a diagnostic thread for the acc? My heat stays on no matter what and it stays on full heat. When I first got the car it was stuck on full ac, now it is stuck on full heat. is there a mix dorr or something not working?

I have checked all pods: they hold vacuum and the rods I can reach all move
I replaced 3 changeover valves, other two are good.

any help is appreciated.

Biodiesel300TD · #2 11-23-2006, 12:03 PM

Your ACC circuit board may have some bad connections. Try pulling the ACC out and then pull the circuit board out and look at it carefully and see if there are any burned spots or anything looks funy. If you find any spots that are burned you may be able to resolder the connection.

lutzTD · #3 11-23-2006, 12:19 PM

i was able to get cold air by jumping 12v to the monovalve..... I am not getting 12v from the connector on the monovalve wire harness...... does that mean bad acc control?

#4 11-23-2006, 12:37 PM

Quote:

Originally Posted by lutzTD

i was able to get cold air by jumping 12v to the monovalve..... I am not getting 12v from the connector on the monovalve wire harness...... does that mean bad acc control?

That does seem to indicate that the monovalve is OK, so the likely problem is the ACC.

jshadows · #5 11-23-2006, 01:12 PM

my ACC problems were not easily if at all visible to the eye. I just followed the soldering instructions from diymb...(i.e. solder everything except IC chip points). Worked like a charm.

RAYMOND485 · #6 11-23-2006, 01:13 PM

1984 300d Turbo
Check The Temp Sensor, Vacuum The Small Opening On The Dash Or
Near The Overhead Front Light They Will Fill With Dust And The Temp Inside Will Go Full Cold Or Hot

lutzTD · #7 11-23-2006, 02:28 PM

I soldered everything with a solder joint with no luck... I am going to try cleaning the sensors....

lutzTD · #8 11-23-2006, 03:24 PM

Quote:

Originally Posted by RAYMOND485

1984 300d Turbo
Check The Temp Sensor, Vacuum The Small Opening On The Dash Or
Near The Overhead Front Light They Will Fill With Dust And The Temp Inside Will Go Full Cold Or Hot

I popped the lower sensor out of the dash and cleaned it but where is the upper one?

lutzTD · #9 11-23-2006, 03:39 PM

from this post

http://www.peachparts.com/shopforum/showthread.php?t=169367&highlight=acc+problem

I found that I should have power at the monovalve when the ACC is in eco with the switch on min cool. I do not have power.... Can someone tell me if there is a relay or something controlling the monovalve? All my fuses are good with the exceptiion of #4 which I pulled out to put in #2

thanx

my123ca · #10 11-23-2006, 04:03 PM

300D does not have an upper sensor. This might help you. Happy Thanksgiving to all.

lutzTD · #11 11-23-2006, 04:09 PM

Quote:

Originally Posted by my123ca

300D does not have an upper sensor. This might help you. Happy Thanksgiving to all.

hi, the esolution teases ne but i cant read it......can you email a better resolution one to me at cobrajet@hotmail.com?

lutzTD · #12 11-24-2006, 06:15 AM

next question.... is there a way to troubleshoot the temp control unit? where is it located and will a "re-solder" job benefit this part as well? looks like the monovalve signal originates from this second acc box. I have re-soldered and freed up the pushbutton box buttons so this is my last resort. otherwise I am going to hook a relay and a switch to the monovalve and have full heat or full ac as my only choices.....

lutzTD · #13 11-25-2006, 11:42 AM

problem solved....this is very irritating... I checked the fuse for continuity first thing so eliminated it long ago. the diagram attached shows I should have +12 at the monovalve pin, soince I didnt the only thing left was the fuse. I spun the fuse in the slot and now I have +12 and the air works fine. I have removed all fuses now and wire brushed the contacts and replaced all fuses with dielectric grease. hopefully this will solve other issues too, like my mysterious cruise control......