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  #1  
Old 11-17-2001, 12:41 PM
someguyfromMaryland
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Unhappy Help needed on 1980 300D Type II ACC

Hello to all,

I'm in urgent need of someone with some real experience on the Type II ACC, which is the one with the servo and the vertical pushbutton unit. I have had no vent operation except defrost for a while. I traced the problem to a vacuum leak behind the console. I have the dash unit out and the shifter cover out, but the center console is still in place. I've checked the vacuum switches (three yellow and one green plastic housing) and they hold fine. I'm trying to check the three way vacuum valves (? I think that's what they're called, they have anodized bronze housings and have two vac lines and electrical connectors going into the bottom) but it's not making sense to me. I'm also trying to check the p/b unit. Are the lines to the p/b unit supposed to hold vacuum when checked or would they always vent because they're rerouting the vacuum to another line?

I don't have the Type II manual so this is not going well. I've patched the system several times and troubleshot vacuum leaks before, but the access and not knowing what I'm looking for are killing me on this one. I thinkk the problem is going to be either the p/b unit or one of those valves, and neither one looks like a very pleasant replacement.

Any and all help is greatly appreciated. This car isn't worth much but it runs extremely well and I want to get the system running again so I can run it rain or shine.

Thanks!!

someguyfromMaryland
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  #2  
Old 11-17-2001, 01:24 PM
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Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
It is almost impossible to work on that system without an appropriate vacuum schematic diagram.

I can tell you that it almost never is the pushbuttons or the vacuum switches or the vac switchover valves (unless they leak vacuum).

The system uses the vacuum switches (not the switchover valves) to shut down the blower and compressor if vacuum isn't on the respective switch. This is probably your problem as the defrost position over-rides the vac switch and lets the blower work in this safety related default possition. All vacuum servos (vac elements) default to the defrost position also without vacuum.

Check that you have vacuum on both lines going to the temp switch at the base of the servo. This switch keeps vacuum (and thus blower) from happening till there is warm water. One line is the source and the other goes to the push buttons and the top of the servo and the vac switch. You will not have blower until there is vacuum in both lines.

If you don't have vacuum to the switch I would individually check each vacuum element first and plug each line going to a leaker. When those leaks are by-passed the system will work (most likely), it just won't blow in the right places.
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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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  #3  
Old 11-18-2001, 09:37 AM
jcd jcd is offline
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Join Date: Jun 2001
Location: Northern New Jersey
Posts: 1,102
Maybe this will help

I have some troubleshooting tech info I received from Larry Bible that I can fax to you.

Also, I have a schematic for a 1977. Don't know if they are the same or not, but I can fax it to you as well on Monday.

JCD
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  #4  
Old 11-18-2001, 11:46 AM
someguyfromMaryland
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Steve, thanks for your reply. That was just the plan I was looking for. I have a George Murphy schematic of a generic Type I systme that is useful, but not totally accurate. It is helpful enough to use with your details and I need to pull the battery and check the lines that route under there. Hopefully I can start putting parts back together soon, this is the furthest I've had to take this car and it's not a pretty site.

JCD,

I don't have a dedicated fax line so I'd have to be ready for it. I think I have enough to go on for now, but thanks!

someguyfromMaryland
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  #5  
Old 11-18-2001, 09:31 PM
someguyfromMaryland
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Talking

Steve Brotherton,

You are the MAN!

I checked under the battery and lo and behold, the battery acid had indeed gotten down there and eaten through the a couple of lines. The problem wasn't too bad yet, only the top yellow and red lines had failed. I patched them and layered the sheath with lots of electrical tape and then tie-wrapped the sheath to keep the e-tape from unwinding. I cleaned off the battery tray and sprayed rustproofing on all affected areas. I'm into the put-it-back-together stage now, as all my vacuum lines are again holding.

I didn't suspect this area because I had checked it about a year ago and there wasn't any problem. Do batteries vent more as they age? I'm not sure why the crud built up so much faster since last check.

Anyhow, thanks for the suggestions. I appreciate the resources this list brings to bear on our individual crises.

someguyfromMaryland
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  #6  
Old 11-19-2001, 09:16 AM
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Join Date: Mar 2000
Location: Gainesville FL
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Now for the bad news. The saga has only started! As the acid leaked through the lines with vacuum in them pieces of disolving plastic and acid vapors got pulled through the vacuum system all the way to the source.

The hardest problem I have ever dealt with on one of these systems was only a couple months ago. A close friend who is shop foreman of a european dealer was working on his neighbors car and had replaced every vacuum element (all lines under battery had been replaced in the past). My assistant spent a morning on it before I pulled him. I spent a half hour tracing vacuum and found that the metal tube in the vacuum manifold on the servo was rusted totally shut. We drilled through it and thought we were done. Another four hours of various seemingly changing events and I told my assistant that I would come in on Sat and fix it. After getting thoroughly confused, I finally did the vacuum circuit tests as the manual directs ( I have fixed hundreds maybe more of these systems in 116,107, and 123 cars and never used the test steps.

On the second test (I think) I found that the other end of the same line had another metal section in the manifold that plugs to the pushbutton assy. It only took me 30 minutes to find it after the test.

The moral to this story is that the acid will follow the vacuum to the source. I have only done repairs to the disasters and I'm not sure what can be done except to blow through the proper source lines, especially at the servo and the pushbutton. I wouldn't blow through the servo though.
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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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  #7  
Old 11-19-2001, 09:55 PM
someguyfromMaryland
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Steve,

Great insights, wish I hadn't heard it though. Everything is back in operation, I repaired all of the lines under the battery and reinforced the sheathing around the lines. I'm looking for 50k more miles out of this daily driver. There is rust in all of the usual places so it's not even close to a candidate for restoration, but it drives wonderfully! That's why I'm working so hard to get it back to a minimum level of service so I can put more miles into it.

If the ACC gets acid rot throughout, it may become a donor car for some lucky person.

someguyfromMaryland
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