Engineer Forensics Automotive, 300E owner
 

My 1991 300E Blower Motor did not work. I removed it,changed brushes, tightned the endplates. I bench tested with 12 volt battery booster. It worked fine. put in car, connected and Nothing. I got 12 volts from the the feed wires. I pulled current directly from the feed connector going to the regulator(essentially bypassing the regulator) and motor runs. Can I correctly conclude the Blower regulator is dead? If not, what next? if so any suggestions minus $250 or so for a new one?

check fuse that is located foward of the main fuse box.
its a rectangular box that containes 1 fuse .might be wraped in tape. the fuse is a flat one.

shavereng
 

The flat fuse appaers to be well and intact. i do not see it as part or the circuitry that begins from three eed prongs on fire wall behind fuse box. I can direct (hot wire) wire the motor from these pins. A harness from these pins brings 3 wires into the motor regulator. ( A larger aluminum porcupine Heat sink) on the back/flat side of the heat sink is a small group of electronic comonents, (believed to be 3 resistors) These are getting xtremely hot on my unit. Once power goes through this monstrosoty it will no longer power the fan.

One would conclude a bad regulator.

Have you checked the signal coming from the push button control unit? There's a 3 prong connector up behind the brake booster (yellow, black and red I think) where you can test.

The PBC's are known to go bad due to bad solder joints. Do a search and you'll find a wealth of information.

Good Luck

Engineer Forensics Automotive, 300E owner
 

Yes I did check the three prong conectors behind the brake booster. I get a signal from there and it will even run the motor when straight wired to the motor. That is why in my mind it must me that blower reegulator as it is the only thing in the circuitry that I am bypassing when doing this. I located a used one for $10.00(used) I just have to drive 30 miles to a junk yard to get it. Of course by it being used, I'll not know if it too is bad in event replacement doesn't correct. I think I'll take Paul's advice and search(again). I would like to find the proper ohm readings on a blower regulator. I believe that thing is probably a series of resistors and should have set values for a good one.

<<I believe that thing is probably a series of resistors and should have set values for >>

No resistors in a regulator.
It is a transistor switched ground.
So, the test is to ground the blu wire after you know the reg has trigger voltage at yellow wire.
You state you have power at 3 prong connector, but you do not tell us if you have both blower power[ 12v] and reg trigger [ 2-8v]
If motor runs with blu grounded, reg is bad............[ only after confirming reg trigger voltage from PB unit]