w126; 300SDL AC vent controls --- HELP!!! - Page 2 - PeachParts Mercedes-Benz Forum

daw_two · #16 05-31-2008, 10:42 PM

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 · #17 06-01-2008, 02:07 AM

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 · #18 06-01-2008, 10:04 PM

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 · #19 06-02-2008, 07:10 PM

2 Yeahs and one Booo:

Yeah, my AC worked today at lunch and also on the way home.
Yeah, my AC is still R-12.
Booo, my dash front vent air only gets down to 64F traveling at 55, and at 75-77F when at idle.

And, I don't think my Aux Fan comes on at all; temperature gauge almost went to 100C when I stopped at the laundry on the way home.

It never ends with these cars, does it. The adventure continues.......

daw_two · #20 11-30-2008, 02:33 PM

You would know it.....it was just warm enough on Friday, that I wanted a little cool air. Does the AC blow out the center vents?

Nope.

So, here I am with a spare ACC unit and trying to determine if it will work. EPCnet seems to indicate NOT.

UGH. My console is in pieces.

Hey Brian Carlton --- you want to give me that advice again??

daw_two · #21 11-30-2008, 02:37 PM

Quote:

Originally Posted by SD Blue

It sounds very much like an intermittent connection in the pushbutton controller. If I recall correctly, you have the controller with the circuit boards arranged in an "H" pattern. Over time the solder connections develop cracks where the boards meet and causes very intermittent problems. Resoldering usually cures this.

However, note that the controller changed, I believe in '87 but it might be '86. A search with ACC and your year model might help determine which one you have.

EPCnet indicates that this unit was "UP TO END OF MODEL YEAR '87"

I bet all the w126 spares I have are for the later years.

daw_two · #22 11-30-2008, 03:20 PM

I'm putting a link to this thread:
ac still not working after ac conversion 87 300SDL

since there is just so much information in it. I'm convinced that "bumps in the road" are causing the ACC unit to operate intermittedly.

Time for a new ACC.

daw_two · #23 12-21-2008, 01:28 PM

Well....guys; the heat has been flakey since I replaced the ACC, so just tore into the monovalve.

Guess what?

The monovalve diaphragm was torn. Got to take the kids out for a ride to see if it works.

BENZSTER · #24 12-21-2008, 07:21 PM

Hope that a new mono valve diaphragm fixed your climate control issue. When was the last time your coolant system was flushed ? Below the mono valve diaphragm within the housing assy there is a strainer/filter screen. This can become clogged after a coolant sys. flush or with a poorly maintained coolant sys. With this clogged it will cause cold/heat command issues as well. Most likely issue would be an intermittant uncommanded heat with cooling air selected. Cooling air will emit from from lower side vents and at the same time heat will emit from upper side vents.