87 300E fan blower needs diagnosis
 

OK guys, I've scoured the archives and found a tidbit here or there on this. I need a little more detail. I wanted to see if my fan blower needed replacing or if it was a switch or something. In one of the posts I found some one mentioned that the fan leads were around the brake booster. I think I found them. Is this a three prong connector that then shoots off with another wiring harness into the blower housing? If I could have some idea of what voltages I'm looking for that would be a help. I hooked up my voltmeter and went inside the car to operate the switches, there was no change when I pushed the fan buttons. Any ideas out there? Thanks in advance.
Thom

There should be a large red wire (+ positive) at that plug that comes from the blower fuse. Also a large black wire that is ground.
The smaller yellow wire is the control voltage from the A/C pushbutton.
IF you measure voltages between the yellow & black wires then you will have from 1V to 6V, depending which blower button is selected.
IF you check the voltage between the red & black then you should have battery voltage.
All with the connecter pluged in of course.

Ok Doc, I think I'm almost there. When I measure the voltage between the black and the yellow wires I do indeed get different values between 1 and 6 volts. Would this indicate that all is well in the control panel and that I should go directly to the blower motor to replace it? Or could the regulator still be at fault? Thanks in advance.
Thom

An Update
 

I finished diagnosing the blower moter and was reasonably satisfied with the conclusion that the blower motor itself needed attention and not the switches or the regulator. I disassembled the cowling taking the windshield wiper out first. Thanks for the article in the archives that showed the step by step process, what a lifesaver. I then got the blower moter out fairly easily. I applied voltage directly to its leads and the motor did nothing. I then noticed that the brushes were worn right down to the nubs. Just for kicks I stick a small wire down into the cage that holds the brushes to see if I could jiggle them into contact with the armature. I then applied power to it once more only this time the motor revved like a demon. Success. Now to get those damn brushes out. Onward we go.........
Thom

Finished
 

I went downtown this morning to search for brushes that would fit this beast. I found them on the first try at an electrical supply company. I asked them how much I owed them and the manager just snickered and said to take them off his hands, he really needed to get rid of this old inventory. I then went home and fitted the brushes which were remarkably close in size but did need filing to fit just right. They worked great, the motor ran like new. I tried moving the armature of the motor from side to side to see if there was slop in the bearings but couldn't find any. Later this evening I finished the job by re-installing the windshield washer motor and assorted peripherals. I estimate that I saved about 500 bucks by doing this myself. When one figures the cost of the new blower motor ($250.00) and labor (!!!!!) then I guess I'm coming rather close with that figure.
Thom