...so what do I do??

I had a battery drain on my 1980 450sl for a while before I was finally able to isolate the power draw to the AC Servo unit (I actually found it coming from connector 33 which is under the passenger kick panel, but that the diagram shows coming from the servo unit). I have read quite a bit about these and know they are a PITA, but I'm about to push forward and try to figure out what the heck is going on with it.

However, before I pull it all out and take it apart, does anyone have any suggestions on what I should look for specifically? I want to try to fix it and see if it is something that can be repaired as opposed to jumping right into a new one. Are there any test, etc that I can do to see a) what is causing the drain, and b) if it can be fixed?

Finally, are there any other components of the climate control system that could be causing this draw?

ANY help would be greatly appreciated!

Zack

If you haven't started that, then don't...simply remove the in-line fuse that is above the fuse box!

That fuse allows the servo to "PARK" when you shut the car off. If you press off first & wait 10-20 seconds the servo will park before you shut it off.

Otherwise take a look at the servo replacement info on the SL forum from unwired tools.

__________________
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Ummm, it may be a little bit too late for that. Yesterday I disconnected the hoses going intot he bottom of the Servo, so I lost all of the coolant that was in there...

...is that a problem, or do I need to refill the coolant before i turn it back on?

Also, can someone explain the 'parking' that the Servo does? I'm a bit confused on what that exactly means.

Thanks!!

The servo arm rotates across a set of contacts, controlled by temperature and blower setting. When you shut the ignition off, the servo is programmed to move the arm to "park" where the power to the hvac system is completely off. If something is wrong and it can't get the arm to park, it will keep trying and drain the battery.

It is extremely unlikely that you will be able to fix this. What has happened is that coolant has leaked into the servo mechanism and corroded it. When they do this, they're gone. Go with a rebuild or the digital gizmo.

You should replace any coolant that you lost.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Alright, I know, I'm an idiot. But this afternoon for some unknown reason I took my acc servo apart (1980 450sl) but I guess I didn't do it right. Now there are a couple of loose pieces that I have no idea where they go, and all of the vaccum lines INSIDE of the unit were unplugged.

Does anyone have any diagrams, pictures, etc etc of the insides of a servo unit so I can maybe put it back together??

Thanks!

Hi there,
I my opinion you won't be able to put it back together again successfully. I also took mine apart, but I waited until after I had installed the digital servo from Unwired Tools. Mine was totally corroded in the gearing, and completely shot. The servo is NOT a simple unit. It was originally designed by Chrysler Corp for their 1970 or so Chryslers, and although it performed adequately in it's original iteration, the Mercedes version was plagued by problems, both vacuum and mechanical.
Do yourself a huge favor - click on "ShopForum up above, then SLforum, then click on the Unwired Tools ad and read up on their digital servo upgrade. They have simplified vacuum diagrams on their website which can be very helpful when troubleshooting vacuum problems. I installed my digital upgrade electronics box inside the cabin in front of the glove box, and the heater valve outside under the hood. It works flawlessly, and provides much better control of the temperatures than the original unit ever could.

__________________
Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C

You are screwed. It is not going to go back together and work. No one except George Murphy at Performance Analysis understands them. It is not worth the coolant, time, and additional mess. Either box it up as a core to send to George, rig up a manual valve, or spring for the digital gizmo.

I work in Winnipeg during the week, and it's getting cold in Canada! You need heat.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

...to do a servo bypass. This is a secondary car that I don't drive very much, but i do want to get it prepped to sell. I have read quite a bit about servo bypasses, but no one seems to say the same thing.

Basically, I'm looking for some way to have it so that I can have both cool air and heat, but I don't necessarily need the auto climate control.

Is there a way to do this, to have both cool air and heat, with a simple bypass?

Thanks!