Heater fan and dash lights quit on 126

[royzell]

Hi, I just got my wife's '84 300SD out of winter storage (it was sitting next to my workshop). It fired right up, there was a lot of condensation under the hood. All the accessories were working, and I left it running with the heater on while my wife hosed off the winter collection of tree needles. I came back later, the car was running but fogged up on the inside. The heater and fan were not working. I discovered the dash lights were not working either. All else seems to be. I checked for fuses, all were OK. One of the relays beside the fuses was quite warm. I swapped it for a spare, still nothing. The replacement relay warmed up as well.

Is there any kind of in-line fuse or relay to the heater fan ? Is there something around the firewall that could have gotten wet when she was hosing it off ?

Thanks

 

[The Warden]

You said that the fuses looked to be okay. Did you physically remove the fuses to inspect them?

I ask because I've found that, sometimes, the end caps on the fuses (that make contact with the prongs in the panel) can break off in such a way that a brief visual inspection will look okay, but in reality you aren't actually making electrical contact. I would pull the fuses and see what the end caps look like.

I believe that the only wires under the hood that have anything to do with the climate control are what operate the monovalve (the valve that controls whether coolant flows through the heater core or not). This should all be between the two firewalls.

I suppose it's possible that, when she sprayed the tree needles off, she inadvertently sprayed enough needles into the fan to stop it from spinning. The fan gets its outside air from the right-side vent behind the hood IIRC (although the 126 may be different). A leaf couldn't really get into the vent, but I could see needles getting in there. Did you get the car up to operating temperature, and if so, did it seem like the ACC unit was responding other than the fan?

The dash lights could simply be the rheostat. They tend to get gunked up inside....I would turn the rheostat briskly to try and clean up the contact points and see if you get any lights. If you do, and if you want to keep the lights at full brightness, it isn't that hard to bypass the rheostat with a jumper wire.

I'll ask around and see if I can find anything else out....that said, I haven't done as much on the 126 as I have with the 123 and 116 chassis cars....

Hope this can help a little bit. I'll try and brainstorm a bit more in the morning after I've gotten some sleep

 

[royzell]

Thanks for the post. I found the MBworld site and posted there as well, after doing a lot of searching through old posts.
Newer 126s (and other MBs) have an inline fuse that can be the culprit. I found something similar on the Left front fender near the front, in some kind of module.
The other option is to pull the right kick panel and underside of dash and check the blower fan itself. I am not getting anything at all from any settings.
The car was running, warm, and fan funning when I left it with my wife.
I'll keep diggin....