Topic: Some ACCII Climate Control Buttons Don't Work

[OLDGOLD]

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.

[UTn_boy]

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. 

[sethkestenbaum]

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.

[OLDGOLD]

Success! I finally got around to taking my 300SD to my mechanic yesterday and I'm happy to report that she's back to normal! From what I can tell all he did was replace all the X and Y fittings as well as any other vacuum connectors in the engine bay. He blew out all of the check valves running down the main vacuum line from the vacuum pump. He also re-routed the shutoff valve away from the 3-1 fitting near the fuse box and gave it its own independent vacuum line. Now, if the locks or CC system loose vacuum, turning off the car won't be an issue.

There could still be a small vacuum leak in the A/C system as the pushbuttons react slower than normal, but the blower kicks on and I don't have to have my compressor running all the time when I need heat. It seems since there was oil vapor being sucked into the system, any piece of rubber in those circuits is now suspect. Everything swells! What confuses me about before is that my rear doors would still unlock even after sitting over night, but my trunk wouldn't get vacuum even when the car was running. Whatever.

Anyways, the car drives much better than it did before and feels more responsive. The vacuum system is so nice if you can keep up with it and I love the idea of having all these features without the need for computers or BUS'. I'll report back if anything goes wrong, but it would seem that just replacing the old hard or swollen connectors did the trick.

[UTn_boy]

When new, the climate control and door locks were separated from the rest of the vacuum system so if there was a leak in the climate control or door locks the car would still shut off.  So I'm somewhat confused about what/why the technician did what he did.  I understand what he did, I just don't understand why he did it since the fail safe he created was there to start with? 

Regarding not getting vacuum to the trunk, a lot of times the gas lid and trunk lock actuators would have a ruptured diaphragm and cause a leak.  People would plug them off at the "Y" connector under the left trunk hinge.  It was a cheap alternative to the correct repair.   I've also seen the vacuum lines have punctures in them under the back seat area.  It'll simply be a matter of testing each line separate from the rest of the system and replacing whatever is leaking. 

Some day you can have all of the vacuum lines addressed behind the dash and that should take care of the leaks for the climate control. 

I'm happy to hear that things are somewhat acting like they're supposed to now.  Definitely a step in the right direction!   

[OLDGOLD]

On the 1980 300SD there are 3 vacuum lines that go into one 3-1 rubber fitting. The three lines are for the shutoff valve, AC and central locking. He removed the vacuum line to the valve and re-routed it. This seemed to fix everything in addition to replacing various vacuum fittings. Maybe other engines had a different setup? I'm the second owner and everything seems to be stock. I could be wrong.

I checked and lubed the trunk actuator with dielectric grease and replaced the fuel lid door pod with a genuine one less than a year ago. I've been fighting the vacuum system for almost 2 years and I'm not giving up now!

[UTn_boy]

Have you checked the vacuum actuators in the doors?  There are three total.  One in the left rear, and one in each right side door.  (opposite for RHD models).  The drivers door has a master vacuum switch.  It simply directs the vacuum where to go when the key or lock button is depressed or pulled up.  This master vacuum switch is noted for leaking.  So check that, as well. 

Given that you have a late model W116, the hard plastic vacuum lines going into each door from the "A" and "B" pillars are also subject to breaking.  As they age they become very brittle.  Opening and closing the doors will cause the lines to break as they're flexed from the doors opening and closing.  So check those, too.  It's very time consuming, but worth it if you find a leak.  The catch is that if you do find a broken vacuum line the whole line will probably have to be replaced.