Once you said some spots looked brown.... listen to Brian...
Have you seen the FSM manual for that rats nest of vacuum and electrical interactivity ?
Just for what you are dealing with at the dash controls...not shared stuff like the evap or blower... just the dash stuff.... I quit counting at 125 pages... and like the other manuals it was translated by a non English as first language person...
Be sure all your vacuum system is in good shape, buy a rebuilt CCU from someone trusted.. THEN attempt to get it all working together...

I've put the thing back in my dash......searching for a reconditioned one. I looked at the hassle of taking off the buttons and that was enough for me.

On toward the next issue. These cars are full of adventures. Thanks everyone for the help.

__________________
daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
No longer selling Cluster Needles Paint
No longer selling New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more

The one in our 300D was acting odd....so I pulled it out, took it completely apart, soldered anything that looked suspicious, and re-assembled it. Put it back in, and it has worked great ever since. (4 months ago) Disassembly/soldering/reassembly took maybe 40 mins....

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

So, I found a spare ACC and installed it about a week ago and all the AC switching to HOT air out of the defrost vents cured itself. Yeah, right!!! Maybe cured itself for one week.

Yesterday on the way home, of course its the hottest day so far this year....same thing happens. So, last night, the original board that was removed got soldered --- took about an hour; good, strong BRIGHT light helps. Darn eyes.

Tonight, try to go to dinner in the big car; started out fine for the first 1500 feet; then hot air. Never could get the AC to come back on --- this is with the backup ACC; not the one I resoldered last night.

I'm leaning toward investigating the mono valve --- maybe just a wiring connection? The weird thing about the backup ACC unit is when this HOT AIR Defrost event occurs, pushing the 0 button does not immediately turn off the blower. Is that weird or what? Of course, the AUTO blower setting doesn't work at all even when the AC is working.

Excuse me, (mam), but can you back up to about 5 feet away, so I can really see you?

__________________
daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
No longer selling Cluster Needles Paint
No longer selling New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more

Well, I just learned the "air intake cover" is NOT the air filter housing...... ... hope everyone LOL on that one. And I thought I was going to take off 2 10mm nuts, lift the air filter housing out of the way, and "jiggle" the connections on Coda's mono valve. Yeah, RIGHT.

Okay, time to put the air filter housing back on, so I can drive it tonight without AC. UGH.

__________________
daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
No longer selling Cluster Needles Paint
No longer selling New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more

Okay, Climate Control experts, I have ONE question for you.

Is there any type of sensor that would detect the outside ambient temperature in the Climate Control circuitry?

Tonight, on the way home, 15 minute drive over the same road as earlier this evening, my ACC worked fine ---- turned it on as soon as I started the car and the vents changed from Defrost to Dash and to COLD. Never did "flip out" the entire way home. The air stayed COLD and it kept coming out the DASH vents. The outside temperature was 76 F.

Any thoughts?

__________________
daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
No longer selling Cluster Needles Paint
No longer selling New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more

So, I found the 3 page, 50 step "AC worksheet" that saumil posted on June 25, 2007. (see this post -- ac still not working after ac conversion 87 300SDL ) Wow! That took some time to compose and also for me to digest. Either my meter is shot or my current 86 300SDL doesn't follow the worksheet. Would a 1986 300SDL be that much different from a 1987 300SDL???

Anyway, I basically concluded that my backup ACC module was not functioning, so I re-installed the original one that I re-soldered (recently). Still the readings are not per the worksheet, but it works. I drove it around the long block and it continued to function correctly.

In saumil's worksheet, an engine temperature sensor is mentioned as one possible culprit. All the times, I've had the issues, have been on rather hot days. Hmmm......

__________________
daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
No longer selling Cluster Needles Paint
No longer selling New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more