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  #1  
Old 07-02-2016, 12:35 AM
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w123 a/c differences

Hello all,

i was wondering what the differences were on the w123 climate control/ac systems.


1. I have a 240d with the manual climate control (the manual knobs and switches). This i think is probably the most desirable.

2. The old style vertical climate control. This has the switches in a vertical order and are usually on the 75-80/81 cars. This is all vacuum controlled and not desirable.

3. This is the one im not clear on. This is the climate control in the 81-85 models that has buttons in one row and usually surrounded by zebra wood (and circle wheel to flip temperatures). I am curious are these easy to maintain fix, are they vacuum or electrical, and are there motors/other annoying things to fix beyond the unit itself.


I have recently redone the entire A/C in my 240d (manual) system. I redid everything but the hoses and evap. I was considering doing the same on the later year climate control... but don't want to go through finding vacuum leaks and other bizzaro motors (besides blower of course).


Thanks in advance.

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  #2  
Old 07-02-2016, 01:00 AM
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#3 is a combination of vacuum and electrical. This system uses the push button unit along with 12 volt/vacuum switchover valves. Additionally there is a temp control module mounted behind the glove box and the auxillary water pump which is mounted in the engine compartment. The switchover valves seem to be pretty bullet proof. The push button unit does have it's share of problems (solder joints) but can be rebuilt, the auxillary water pump can go bad resulting in burning out the push button unit (the aux water pump should be protected with an inline 2 amp fuse). The temp control module is fairly bullet proof. The vacuum pods under the dash which control the different vents can go bad (ruptured diaphrams) but can be replaced or repaired. Unfortunately, in order to repair/replace most of the vacuum pods the dash must be removed.

Any sort of vacuum leak can cause a malfunction in the climate control system.
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  #3  
Old 07-02-2016, 01:49 AM
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damn. That is unfortunate to hear. I assume switching this over to the manual system is really difficult to do?
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  #4  
Old 07-02-2016, 09:32 AM
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I think really difficult to do is the understatement of the century...
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  #5  
Old 07-02-2016, 10:32 AM
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You only show one car in your profile..
are you talking about converting another car to the manual control which you correctly identify as the most desirable ? ( like I have )...

The trouble shooting section on those dash buttons in the MB AC FSM is 80 pages long...

You can make that system much simpler... if you do not mind the buttons not working... and making some non standard manual controls... so the question starts to involve things like ' restoration esthetics'' or USEful AC working in a really old car...

What exact second type AC car are you talking about ? Does it have a huge fiberglass box in the engine compartment ?
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  #6  
Old 07-02-2016, 12:01 PM
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i am thinking about doing this on an 83 300cd... Also my friend's 84 300td's AC does not work and both of those have at least the same head unit for the climate control (the one row of buttons with scroll wheel).


Want working A/C. Don't care about asthetics so much.
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  #7  
Old 07-02-2016, 12:09 PM
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Location: central Texas
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I think the first thing to do on both...
is to test the systems for leaks...
both of the AC refrigerant
and the vacuum control system...
then make decisions from those results...
might not take a complete change over to get one or both working.. OR might could work until cooler weather to work on them...

Just FYI... there are two systems which use the vertical wheel on the dash... system ll and system lll ... your manual is system l.
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  #8  
Old 07-02-2016, 01:44 PM
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System 3 isn't horrible, but it does take some work to rehab a worn out system. I think for about $350 to 400$ in parts you can refurbish the "control" side of the system (as opposed to the refridgerent loop side. The refridgerent circuit is pretty much the same on all w123's I think, so I am not going to go down that rabbit hole.

HVAC pods - one of the members here sells rebuild kits for these. I am blanking on his name. Roughly 40$ for all new diaphrams. Pulling the dash to rebuild them is not 100% necessary, but honestly it's not as bad as people make it out to be.

Switchover/changeover valves (i get them mixed up). Not incredibly failure prone. I had 2/5 failed, replaced those with ones from a junkyard. Can be accessed with the dash in place.

CCU - yours may be burnt out. Mine was, tried to mix & match parts from another unit with bad switches, not quite compatable. Bought a refurbished one.

Aux water pump - easy to replace, don't recall price. Add a 2a fuse, easy job.

Cabin temp sensor - can actually be rebuilt for about 5$. I think I have instructions posted, if not ask me and I will be glad to help.

Monovalve. Huge pain. Find an original core that works and rebuild it.

Personally, I prefer to have an original system that works. Not sure how difficult a conversion to manual controls is. Might save you a bit of money, but I doubt it's easier than rebuilding ACC3. Though to be faie I have some electronics skills that others likely do not have. And I am really picky.
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  #9  
Old 07-02-2016, 03:55 PM
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Here is a couple threads on swapping over to a manual system.
Too bad crazy4diesel deleted his pictures.

http://www.peachparts.com/shopforum/diesel-discussion/352917-manual-climate-control-swap.html


Charlie

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