Author Topic: Some ACCII Climate Control Buttons Don't Work  (Read 85 times)


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Some ACCII Climate Control Buttons Don't Work
« on: 05 November 2019, 07:38 PM »
I have a 1980 300SD with the upgraded Sanden compressor and Unwired tools ACCII Upgrade kit. A few weeks ago the “Auto Hi” “Lo” and “Bi Level” buttons no longer work to start the blower for heat. The defroster works and the blower/compressor both kick on, but not the other buttons. I replaced the switch block behind the buttons as those can burn out, but it’s still not working after replacement.

However, around the same time my diesel shut off valve on the back of the IP finally went out after leaking oil for some time. I had an inline filter in place to catch the oil as money was tight. My engine took about 20 seconds to finally stumble to a stop after the key was removed from the ignition. This was shortened to about 5 seconds after replacing, and yes the valve tested good. I then removed the brown vacuum line from the 3-1 rubber vacuum fitting near the fuse box and reinstalled and that shortened it to about 3 seconds. All I did was pull it out and put it back in a little further and this helped somehow. These cars are a mystery sometimes.

I know these are two different issues, but I feel like they are related. I’m pretty sure its a vacuum issue in both cases, but I have to add that I also had the steering lock and ignition switched replaced and replaced the vacuum lines on the steering lock as one was swolen, so no leak there. The diaphragms in all of the doors/fuel lid door are good. The trunk was good last time I checked while ago. So I’ve kept my vacuum system up as much as I can, but I’m just wondering if any of you have run into any one of these issues, or maybe both? Thanks in advance.


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Re: Some ACCII Climate Control Buttons Don't Work
« Reply #1 on: 08 November 2019, 03:36 PM »
The fact that only defrost makes things work is indicative of a massive vacuum leak somewhere.  The system was designed to work on defrost regardless of what all else didn't work as a safety precaution. 

The two issues you're having are two different issues, but you shouldn't feel that they're related.....they ARE related.  Both the climate control and the shut off vacuum box share a common vacuum supply either from the engine (all v-8 engines and early/European M-110 engines) or from the vacuum pump (on diesels and asthmatic U.S. spec M-110 engines). 

The addition of the aftermarket climate control assembly is completely useless when vacuum leaks are present.  Since it seemed to be working before the vacuum leaks I'd start testing each vacuum circuit.......paying particular attention to all of the vacuum actuators and the electropneumatic on/off switches behind the glove box, (yellow, white, red, and green in color)  and sometimes mounted behind the pushbutton unit to the right.  Obviously, all vacuum connectors are suspect until proven otherwise. 
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1973 300sel 4.5, silver blue metallic/blue leather
1976 280s astral silver/blue MB Tex
1978 450sel 6.9 Euro, Anthr/velour


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Re: Some ACCII Climate Control Buttons Don't Work
« Reply #2 on: 10 November 2019, 11:14 AM »
Oldgold, My w116 came with the same HVAC issues where the defroster works fine but the heat and AC are otherwise non-functional. I haven't gotten around to checking each vacuum circuit -- and the car keeps throwing other more pressing issues at me. I suspect there is a disconnect somewhere in the HVAC vacuum circuit and a slow leak in my door lock circuit.   If you would be kind enough to share your troubleshooting process for the vacuum leak, that would be great.  I know I would benefit from it.
Seth Kestenbaum
1929 Model A Ford Phaeton
1969 VW Bug Convertible
1980 300 SD Turbo Diesel getting fixed up
1980 300 SD Turbo Diesel rusty parts donor car