82 380sl Hvac

[BBAY]

Per suggestions, I purchased the manual to attempt to de-bug the non operating HVAC system on my 1982 380SL. I have a non-running blower and a constantly running circ pump. The diagram indicates that fuses 6 and 7 in the main fuse panel serve the climate control system. There is also a fuse indicated in the 'auxiliary fuse panel'. Can't find it. Hints. Thanks BB

[ctaylor738]

I looked on the CD, but could not find a wiring diagram for the ACC for the 1982 and later cars. The only diagram is the power and ground distribution, which is sort of an overview. Did you find the wiring diagram for ACC?

The blower should have a straight-through connect on DEF. If it doesn't work on that setting, I would get at through the cover at the base of the windshield and put 12V to it. If it still won't turn, it is probably brushes, which George Murphy sells quite reasonably.

[BBAY]

Hi Chuck.
Thanks for the reply. I did the normal troubleshooting, which proves the blower and resister bank is good. I followed the guidance in the manual which directs me to ground the engine cold lock out switch and do an ampere draw test of the blower motor. The following directions make it clear just how D.Y.I unfriendly these cars are. I'm paraphrasing, but the guidance is this.." If the blower motor does not run, replace the motor control module, the dash control assy, and the blower motor in turn until the blower works". Wow..replacing major components until the problem goes away...I feel just like a factory tech. (;-)
I took the car into an independent MB shop and their opinion was that there were vacuum leaks under the dash that were preventing the blower from running. They assured me that if I left the car with them that they would trace those leaks and correct them "No matter how long it takes". Scared the hell out of me and I ran like a....thief?...well I left anyway.
I did check the manual again and could see no relationship between the blower run function and vacuum operated devices. Did I miss something?
Thanks again for the advice. BB

[ctaylor738]

Hey Bruce -

That's what I was trying to say - the detailed ACC wiring diagrams are missing from the CD for the 1982-on. For the earlier years, there is a massive amount of information on current and vacuum flows - different diagrams for each setting of the pushbuttons. The one diagram provided for '82 on is just a summary of current flow and ground.

My suggestion would be to call George Murphy at 865-482-9175 and see if he has some that he would send you on the chance you might buy a control module from him. If you have the diagrams, it is possible for a talented amateur like you to find the problem.

So for most of the settings, vacuum is needed to close various switches before the blower will come on. But, at least on my '81, if you hit DEF, you are supposed to get a direct feed to the AC and the blower, bypassing all of the control modules. I would think it is the same on the newer systems, so if you lose a control module you could still clear the windshield.

I think that the 2A fuse is a mistake for the '82-on, and is used in the earlier cars to allow current to the servo when the ignition is turned off - it moves to a "park" position.

I am not making this up.

[ctaylor738]

Pick the 1986 560SL when you bring up the CD, and look in the Wiriing Diagram. The current and vacuum stuff starts on Page 301.

But it looks like they changed it - the DEF power goes through the control modules and vacuum system.