Climate Blower Switch... is it bad? '86 300E - PeachParts Mercedes-Benz Forum

DEPRIEST · #1 03-18-2007, 09:03 PM

Hi Guys,
I haven't dug around too much into this problem yet because I'm not sure where exactly to start. I have an 86 300E which is running well. The only problem is, the heater/AC motor doesn't always blow. Some times it does, sometimes it doesn't. So it's like this. Sometimes I get into the car, begin to drive and the fan won't kick on. I'll be driving for a while (the timing isn't consistant... sometimes within 5 minutes, sometimes within 20 minutes) the fan will just begin to work. So there's a bad connection somewhere.

Sometimes when I'm driving and the fan isn't going on, I punch the switches on the dash in an attempt to get it to work. This doesn't do the trick. I was thinking the dash panel was giving up the ghost, but I wanted to get your opinions first. Is there a culprit point that often gives out?
Thanks

brewtoo · #2 03-18-2007, 10:38 PM

I had an '86 do this same thing.

Turns out that the plug up on the firewall was dirty. Pulled the plug off and put it back, and it solved the problem.

The plug is on the driver's side of the firewall, three wires, you can just reach it.

See if that helps.

DEPRIEST · #3 10-21-2008, 05:55 PM

It's been a while with this, and I'm finding another winter approaching and I need my heater. I didn't mess around with this last year.

Where is this wire/plug? I looked all over and couldn't locate it. The Haynes manual was no help in this department. Is it way down in there? Is it in the main compartment with the engine or is it in the triangle shaped compartment where (opposite the battery)

Thanks all, I appreciate the help.

brewtoo · #4 10-21-2008, 07:28 PM

It's about right in front of the speedometer, up high, to the left of the expansion valve.

cbdo · #5 10-21-2008, 09:28 PM

Other possibilities:
1-Fuses on these cars can degrade over time and appear to be good but actually be going intermittent. Replacing the fuses can fix a number of weird electric gremlins. Ideally, try to avoid aluminum ones as they corrode more over time.

2-The circuit board in the control unit can develop cold-soldered joints as it ages; do a search for how to take it out and re-solder the connections on the board, which is often effective and took me about a half-hour.

DEPRIEST · #6 10-25-2008, 01:01 AM

Thanks, that's all good advice. I tried the plug, like brewtoo suggested, but with no luck. I'm taking my car to my mechanic, who's very good, to have him swap out my ignition tumbler. (can you believe my 22 year old car has more than one problem?) I'll have him take a peek at the fuses while he's in there.

I fear I may be doing this job:
http://www.peachparts.com/Wikka/W124BlowerMotor
soon. I'll get to the bottom of this problem... with this forums' help...