I have a 1994 S500, and bought it a few months ago. I have a question about the blower speed for the climate control.
The heater and A/C functions as it should, with the exception of blower speed. It seems that the blower seems to run at one speed only, a med-lo speed. The unit EVENTUALLY cools down or heats up the car, and the airflow moves to the appropriate spots when different control buttons are pushed, but there is no High speed.
Is there a fuse or relay that is dedicated to the high-speed blower function??
Or any other ideas on what might be the cause/cure of this??
Thanks,
Barry

You undoubtably have a bad blower controller. This is a very common problem with 140 chassis cars. That is unusual as vitually the same device is used on 124 chassis with no failures. I attribute this to the size of the heat sink on the 124 models. Strange how the better part is on the cheaper older car.

The blower controller is just a huge power transistor. It has power, ground and control signal coming in. It's output is the voltage to the blower itself. diagnosis is to verify the control signal. I think it is a 0-5v low to high signal.

The controller is located on top of the blower accessable from under the hood after removing the covers on the passenger side.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Thanks, Steve.
Any idea how expensive a blower controller is and how hard is it to replace??
I "used" to be able to do almost all the work on all the cars I have owned in the past, but this bad boy is amazingly complex.

Thanks,
Barry

Seems like they went for around $250. Thats from memory. They are relatively easy to replace. I haven't done the job myself. I only do diagnostics. Seems like it takes about an hour.

If you are interested in the steps, email me during working hours and I'll put something together.

BTW, Michael Haven (a member of this forum) owns a shop in Houston. He is one of the finest technicians I know. His business is MPH Automotive. We are members of four tech only groups and both our shops are Bosch Service Centers. I would get to know him.
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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[This message has been edited by stevebfl (edited 04-23-2000).]

Thanks again, Steve.
I have already submitted a part qoute to a couple of different places.
This does sound like pretty much a DIY job, as I have already replaced the filter over the blower and that took about an hour, as you said.
I will keep Michael in mind, as I also have an SRS dash light that stays on for exactly 2 minutes upon startup. It's not a big deal, but it would be good to have it made right.

Thanks,
Barry

Just wanted to say thanks, Steve.
The controller WAS the problem, and it took about $180 and an hour of time to replace it.
It works great!!!
It's ready for the Houston summer now.

Barry