Version II HVAC problem - Mercedes-Benz Forum
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post #1 of 24 (permalink) Old 06-26-2019, 06:46 AM Thread Starter
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Version II HVAC problem

I have been searching everything I can find on what I believe is Version II of the HVAC in R107 SLs to no avail. My blower only works on speed I & II, not III & IV. Dealer says I need a new Blower Motor Regulator for $1094.72. Yikes! Problem is, the Blower Speed regulators for sale used every where (Bosch GeblaserRegler 0008221103) are for later models with climate control systems. I am unable to find anything similar under my dash or near the blower. All the prior posts on this topic seem to reference the later systems. I have pulled the blower and the attached pre-resistors and everything tests OK, all four speeds. The electrical diagram I was able to find of the early HVAC system shows NO blower speed regulator, only a direct connection between the dial on the console and the Pre-resistors. Does anybody know if this is correct? If so, can the five position (including "off") rotary switch really be $1K or was the mechanic making a WAG based on experience with 560SLs? Any idea where I might find a replacement switch(new or used)? I'll be digging into the console soon anyhow to return to the original style radio (Becker Europa Kurrier as shown in the first diagram) so that would be the time to replace the switch. Two diagrams are attached which show what my console HVAC controls look like and the HVAC electrical diagram. Any help would be greatly appreciated.
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post #2 of 24 (permalink) Old 06-26-2019, 08:38 AM
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Edit: Ok I had some more time to re-read your wall of text. For the future, paragraphs please.

Assuming your profile is correct (a 5 speed euro 280SL) and from from that picture, you have ACC1. IE the one with manual controls.

ACC2 is the dreaded Chrysler servo that leaks everywhere. My 380SL has ACC3 and everyone who has a post 1986+ vehicle has ACC4.

ASSuming what I have written above, your mechanic was making a wild ass guess and frankly at the prices they're quoting you an expensive one that might be incorrect.

Now I may be wrong. Does your climate control look like the one you posted in the image above or does it look like this?




(Ignore this bottom bit because I think you have version 1)

Contact this guy http://www.cruisecontrolrepair.com

Forum guy by the name of JamesDean. He repairs these old boards . Most likely a bad solder joint and or a bad capacitor, all of which he will fix and replace.

You will need to remove every component of the system and mail it to him . I think it took him a week to fix and mail back. Great prices and you get to keep your ad units.
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post #3 of 24 (permalink) Old 06-26-2019, 12:34 PM Thread Starter
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Thanks for the link but this is the same thing I mentioned in my earlier post: according to the circuit diagram, I don't have an "old board" to repair. His info seems to be oriented towards 1981 and later systems with "climate control" rather then just manual HVAC. I have searched and can find none of the parts he shows on his web site. I'll try tracing the wires but that's almost impossible without removing the dash, not something I'm looking forward too. If no one has run into this before, I guess I'm going to experiment a little.
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post #4 of 24 (permalink) Old 06-26-2019, 01:46 PM
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I was missing one speed so I replaced the actual switch attached to the fascia (the left round knob) I'm assuming yours looks like the fist pic. It was less than $100 as I recall but that was a few years ago. Sorry I don't remember where I bought it. My RHD has the old lever system.
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post #5 of 24 (permalink) Old 06-26-2019, 03:44 PM
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One thing for sure. You don't have the blower control unit 0008221103.

107s used four types. Manual AC, lever system, which can appear in most ROTW years and models. Automatic Climate Control ACCII which is the Chrysler design used in 1978-1981 US and some ROTW models. ACCII 1982-1989. There are two versions of ACCIII. The fourth is one I have seen on some ROTW models, mainly '84 and '85 280SL models.. It has two rotary switches, two dials, and two rocker switches.
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post #6 of 24 (permalink) Old 06-27-2019, 06:40 AM Thread Starter
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The pictures below show what the manual is calling the 1st and 2nd versions of the climate control elements. I have the 2nd, four sliders and two knobs, no push buttons or lights.
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post #7 of 24 (permalink) Old 06-27-2019, 08:12 AM
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First things first . . . don't spend money on this yet.

It sounds like you found your blower motor resistor package mounted to the firewall in your engine bay just right of center. The harness that attaches to that point comes directly from the blower switch. You also said this:

Quote:
I have pulled the blower and the attached pre-resistors and everything tests OK, all four speeds.
As you and @Aussiemerc correctly stated, the problem lies with the switch or the wiring from the switch to the resistor pack with one tiny little detail left open to speculation on the resistor package, the overheat circuit. Give me a little time to review that.

If you decide to dive into that HVAC panel, start by removing the ashtray. Next, remove the 2 screws that hold the ashtray frame in place. The frame is removed by pulling on the right side, allowing it to deform a little. There is a 2 pole plug on the left side that must be removed - don't panic if that plug vanishes, it is easy to get to later. I have not worked on the ROTW (rest of the world) version of the HVAC system that @rowdie outlined in his post. It seems like you have this version. There may be two small machine screws in the ceiling of the ashtray cavity that anchor a clip for one or both or those knobs on the panel. I don't know if ROTW models have this - they are on the temperature/vacuum switch (AC switch) on my car.

Pulling that HVAC panel is a delicate operation because the trim around your slider handles is very prone to breaking - even new ones (which probably have been sitting on a shelf for years and are no longer new). Those have to come out to reveal screws that hold the panel in place. I use picks to unscrew the metal nut behind the knobs.

Once that panel is off, a continuity check will reveal a wiring integrity problem. The same can be done on the pins of the switch.

Brad Cushman
73 450 SL
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post #8 of 24 (permalink) Old 06-27-2019, 08:31 AM
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Second pic. in post 6 is hard to see. I think those are both versions of the manual system. The Euro system I described is pictured here.
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post #9 of 24 (permalink) Old 06-27-2019, 11:07 AM Thread Starter
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That's definitely not what I have Rowdie. As I mentioned earlier , my system looks exactly like picture 2 in post 6 and picture 1 in my initial post. I have pulled the console and removed the switch body and tested it and the only position that has continuity is what appears to be speed II which is the only one that works. So it looks like I found the problem but now, where do I get a replacement? As you can see in the pics below, no part number can be seen. I've yet to try my dealer but plan to stop there tomorrow. Any other suggestions would be appreciated. Also, does anyone know the size or where you can get the tiny bulb that lights up the switches?
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post #10 of 24 (permalink) Old 06-27-2019, 12:49 PM
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You have the same one that I saw in an '81 280SL. I think the switch is A 107 820 05 10.
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