Does anyone have a link to how to repair the ACC on a w123 300d 1984?
Photos would be great.

I've seen the link on re-soldering the pins but is there anything on the web that talks about testing the circuitry?

I'm a hack with my multi-meter but I might be able to fix my broken ACC with some help. The mono-valve is good but for some reason it starts blowing hot air when the dial is set to min. I usually have the 2nd button to the right pressed. I know that the defrost button will blow heat regardless of the dial setting.

Any help would be great.

Thx

Pete

I had ACC apart in the identical car some years ago. There are no repair instructions of which I am aware beyond what you can find here or on other similar forums. Your hot air symptom can be caused by a broken or disconnected temperature sensor (the one in the middle of the dash).

You say your system blows hot air when the temp dial is set to MIN? What about other settings?

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

There are 2 things to check. The fuse that controls the monovalve. Also put a voltmeter across the terminal of the monovalve and see what voltage you get.

1) 12V - it is NOT calling for heat.
2) 0V - it is calling for heat.

If you get 0V then it is either a blown fuse or CCU is not functioning. A lot of the times I do a simple test like this.

a) Set the temperature to Min
b) Put the meter across the monovalve
c) It should measure 12V with car running.
d) Set temperature dial to Max
e) The meter should drop to 0V within 5 seconds. Reset to Min if necessary

This shows at least the CCU is sensing the dial setting.

Good luck.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

Thanks for the replies. After reading many posts on the ACC, I was looking for my temp sensor and I can't find one on my dash.

Here's a picture of my dash.
On other 300d's I've seen a little black plastic slotted cover on the top of the dash between the front 2 vents. Mine doesn't have this.

I will test the voltage tomorrow.

Does the sensor attach to the ACC?

Any ideas?

Thx

pete

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1984 should have a sensor where you have none, under a little grille as you describe. What country are you in (you can add location info to your profile -- it shows up in the upper right corner of your posts)? Was your car specially imported or something?

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

I'm in Baltimore MD but the car was from Georgia.
I don't think the dash was replaced. If I get a sensor at the junk yard, will it attach to the ACC?

I could cut a little hole in the dash with an xacto knife and install a sensor.

Thanks.

pete