80 300d blower speed control?
 

The challenge of "manualizing" the climate control on the 300D has begun. Rats and PO(s) did a number on the vacuum lines. I now have simple toggle switches to steer the vacuum to the flaps to direct the air. Everything else was removed. I still need to regulate the fan speed and re-route the coolant to the heater core thru a valve.
The module behind the glove box... is that what regulates the speed of the fan? I see two power transistors on the pcb so I assumed so. I can't find any large wire wound resistors in the car to slow the fan speed. I may try an electronic motor cotrol using the old temp thumbwheel pot as the fan speed adjust.
Man, I bet with the pump, ACC and vacuum lines gone shaved 35lbs. Better MPG!

Happy Holidays Ya'll,

Dan

82 300SD parts car if anyone needs anything... let me know.
84 500SEL for sale cheap.
bunch of other MBs...

Good luck, you are going to need some good wiring diagrams to figure it out...

Actually, the "new" wiring is very basic. Toggle switch(s) apply 12 VDC to each of the old existing vacuum switchover valves allowing vacuum to pass to the appropriate vacuum elements (main air, recirculate, defrost, legroom... flaps)
I never figured out how the fan was controlled. So, I may get creative and build a solid state speed control. I thought using the old temp thumbwheel would be appropriate.

I would always recommend fixing the original MB climate control if possible. In this case the MB's CC was beyond economical repair and the car was obtained for next to nothing. Didn't have much to loose. So, what the heck...or, was that...hack.

The later 300D's like my '83 have a set of "springs" in a cage or box on the passenger front fender well. These are the resistors for fan speed control.

Whiskeydan,
Is there any chance you are documenting this process via digital photos? I also have an '80 model that had the ACC bypassed when I got it. I just have a toggle for the compressor and a toggle for the fan.(high only). Air comes out of dash and defrost, all the time. And no heat at all. Very crude at this stage compared to yours. I bet your information could help out a whole lot more than just me.
Jimmy

When I get alittle further along and feel like it not one of those "projects gone bad" I'll put something together for those to follow if interested.

Wow, It seems like there's alot of folks from Texas here. I'm north of Dallas. How about a meet sometime in the future? In my travels around here I have located some good used parts sources.

I am glad I found this group. I have been lurking for sometime and felt like this was one of those things I needed to do(manualizing the heat/ac) to pay the group back for all the info I have received from it.

Dan
(searching for a good TD)