mercedes 1986 300e blower fan problem
 

hello to all have had my blower motor changed,each time blows the fuse back to shop 4 times.mechanic ran a seperate line from fuse box and added a 30 amp fuse said it would be fine,I have noticed that the fuse holder gets very hot any advice i am afraid that it might cause a electrical fire.

Hmmm, I assume we're talking about the blower fan for the cabin and not the blower fan for the radiator. My '86 had a blower fan issue where the bearings were too tight and it took too much current to turn the blower motor. Though the fuse never blew, I did notice how hard it turned while trying to clean a plugged evaporator. So, is the motor free from obstructions and binding. If the fuse opens, that's your safety valve, so an electrical fire doesn't occur. Does you mechanic know what the current draw is from the motor? What was the original fuse rating? 30A is quite a bit of current when you think about the alternator only puts out about 65A.

The reason a fuse blows is because there's not enough (electrical) resistance (short circuit) or there's too much consumption of current. Basically, there are too many electrons (current) trying to ride the bus (wire) at the same time.

Hope all that helps.

Michael B.

Ok, I finally got a chance to look at the wiring diagram. Fuse #12 supplies the blower control unit. Here's what I'd do... connect a wire from battery to the fan + (probably the red wire) with a ammeter and circuit breaker in series and measure the current draw. If it's considerably less than the original fuse rating of 25A, then I would suspect the blower control unit and not the blower fan motor. If it is as high with it connected as factory intended, then the blower fan is suspect, regardless if it's new.

Hope that helped.