Blower Motor Issue
 

Hey - anybody know where the resistor that controls the blower motor for the climate control system on a 1990 300TE is?

Just beneath the blower motor.

blower motor resistor (regulator) - can it go bad or increase voltage draw?
 

First: where is the silly blower motor resistor (regulator) located on my 1986 190E 2.3-16v? - I found it behind the plastic panel behind the battery.
Second: can it go bad and cause an increased draw on the charging system?

I have a new alt, new voltage regulator, wires checked good, and the voltage meter in the car and my DMM still show that the charging system is struggling to keep up. At times with the a/c on high and the lights on the alt is charging under 10 volts.

As i turn the fan blower up the voltage draw goes way up.

Can replacing the battery charge idiot lamp with a LED lamp cause a charging problem?
I am stumped as to the problem.

Bad regulator I would guess first if not the alternator. No an led will not cause the issue.

The "regulator" is under the blower motor. If you call it a resistor you probably wont locate a replacement :).

regulator
 

Are you saying that it might be a bad blower motor regulator (resistor)? I was wondering about that. It just seems that the blower being on is drawing an awful lot of juice. Anyone have the amps the blower motor should pull at different speeds?
The voltage regulator and the alternator are new and have been changed out for new parts once at the shop already.

blower regulator
 

so far I have found that I can get the blower motor regulator for about $90.
I am still not sure if it is the problem. need to find the list of normal amperage draw for the different blower fan speeds to check to see if mine is drawing too much juice or not.

wiring diagram
 

Got out the wiring diagram book during breakfast. Looked up the charging warning lamp. Looks like the current for the blue/white wire to the alternator stator passes right through the 2 watt bulb for the charging warning lamp. I changed out all the warning lamps with led bulbs. Easier to see and notice during the day and a nice bright clean colorful light as opposed tot he washed out color of the OEM bulbs. Only problem is it looks like the super low resistance of the LED bulbs and low draw has droped the needed juice to make the voltage regulator control the charging fuction properly. Was to go! SO, going to reinstall the OEM bulb and see what happens this morning. Wiring diagram seems to support the theory. We shall see.

Just as a note, it also looks as if the current coming out of the bulb for the charge warning lamp goes to the ABS control unit.

Yes. Replace with the proper wattage bulb. The alternator field is energized by the bulb circuit. Mark

battery charge bulb circuit
 

Thanks for the confirmation. I thought from the wiring diagram that I got out this morning it looked like the bulb circuit was controlling the field in the voltage regulator. WHo would have thought? SO if the bulb burns out, you get a faulty charging system, nice. Oh well, I got the bulbs after breakfast and I am out to replace the bulb now. Too bad the instrument cluster is a hassle to pull, I am going to try my best to slip a blind hand up the back of the cluster and reach the bulb...maybe I can get my 5 year old to do it for me? Oh, well, at least the mystery is solved.

the blower motor will draw 30amps at full speed.a worn alternator or bad wiring [read old and corroded] will not allow necessary amps to battery.i have replaced the wiring loom from alt to battery to help cure this problem before.

still not charging enough
 

I got the correct 3 watt OEM bulb in the battery charge warning lamp.
I also tested to see if the amps are increasing enough when the loads are placed on the charging system. Amps start out at about 17amp draw with nothing on, engine running, and car in park at idle. Then as I turn things on amps go up. With ac, blower on high, radio, headlamps on, engine running at idle in park..the amps go up to about 59amps However, the battery is still not staying at around 12.5-13 volts. It drops down to 11.9 or less

you might also check that the belt is tight on the alternator pulley.it is the smallest one there and the first to suffer if belt not tight.

I will check the belt
 

I planned on checking the belt tightness today too. I pulled the alternator the other day so it might not be tight enough. I am just always concerned about getting it too tight and messing up the tensioner. Thet contraption is one of the few things that MB designed that I absolutley hate! Hate to tighten, hate to loosen, hate to replace, I just dont like the thing.

i hear ya brother