accessing A-C/Heater Blower Motor 1986 300E (W124)

[thurat]

Hello, I have a 1986 Mercedes 300e that the blower is not working on. First I am trying to figure out where the physical blower motor is located and how it is accessed. Second I am hoping, someone might have had or know what this problem is and how to correctly fix it.

Most time the blower will not come on for heat or air at all and it seems that the only time it does come on is after that car is quite well warmed up. If I have drove it for 30 or 40 minutes and then turn the car off and restart then the blower will come on and the system acts very close to normal. Of course my normal commute is less than 30 minutes so I do it without heat/air. This has been going on for about a year steadily getting worse.

The majority of the time the controls do nothing. You can press them and turn them any way to want and it makes no changes. Nothing comes on, nothing happens, no clicks, noice, air, or any other indications that something is happening. I would not want to haul it in to my local dealer as I don't want to get into a situation where I have to keep spending money to get out of it.

Thank you everyone for any help or insight you can give.

[lee polowczuk]

have you tried backing off of the ignition key just a hair....?

other than that it sounds like the brushes on your motor are going south

[Gilly]

The blower motor is under the wiper assembly, so you need to get access from under the hood at the base of the windshield. The wiper arm comes off, then the trim at the base of the windshield (all the way across), then the air intake screen, then the windshield wiper motor and linkage assemble, then you can take the blower motor cover off and get to the blower motor.
And I agree with the previous post, more than likely bad brushes in the motor, I'd recommend a new motor assembly and transferring the blower cages over to a new motor.
Gilly

[thurat]

thank you for the input. I've dealt with bad brushes on electric motors before and can not recall any cases where you get good operation of a motor after the system has been on for a while. Can you please explain HOW or WHY this is happening. I'm just a little confused. Also is the AC blower and the ACC blower the same? The information I'm able to find on this is a little confusing.

Thank you again.

[Gilly]

My thought is that when the brushes are worn, if it's not working at first, but take the car out and drive it and hit a few sharp bumps, it will jar the brushes and the motor might start to work.

There is a large strap fuse on the left strut tower (near the brake master cylinder) it looks like a tiny black coffin, lift that cover up and there is a strip fuse for the blower motor, you can test for voltage there, so you can be sure voltage is making it to the blower motor, quick confidence-booster that you are on the right track.
Gilly

[lee polowczuk]

somewhere on here there is an excellent post with pictures on how to get to and remove the motor...

easy job, just a bit time consuming ....first time 2.5 hours..... going slowly and referring back to the pictures..

now i can do it in about 1.5 hours.

[Cal Learner]

Yes, definitely, before you go to the trouble of removing bits and pieces to get to the blower motor, inspect that strip fuse very carefully. They do break. If that's it, 50 cents and 30 seconds later your blower will be back in business.

[Ferdman]

The 30-amp strip fuse develops a hairline crack across it that is very difficult to see. Loosen the 2 Phillips head screws and remove the strip fuse to inspect it.

From your description of the problem it's likely that your strip fuse is cracked. When the under-hood temperature increases the heat causes the strip fuse pieces to expand slighltly and make better contact and the blower motor functions.

[thurat]

Thank you everyone for your input I'll check all of that. I'm thinking the problem is in a control somewhere, not a cracked fuse or bad brushes because (and please correct me if my thought process is in left field) once you have given time for the car to warm up the motor doesn't just kick on. You have to shut the car off then turn it back on. It doesn't start working while you are driving or after a bump and summer/winter doesn't seem to change anything.

If it is a control unit or part, what one might cause this, where would it be located it, what would it cost/take to fix it?

Thank you again,
Thurat

[lee polowczuk]

do the other tests, first......

[thurat]

Hey, I can't find the fuse on it (some change?) but I did find the connections. If I feed power directly to the motor (red and yellow wires) it works fine. I'm thinking one wire (red) is the hot wire and the other (yellow) is a control wire (rheostat). I still don't know what the true problem is but it is not the blower motor. The coupling, which was where the fuse should be, had three wires: Black, Yellow, Red. Nether the Yellow or the Red wires are getting power with the car running and the system turned on.

Does this mean anything to anyone?

Thanks,
Thurat

[Cal Learner]

Here it is.

[Randy]

On my 420, the heater blower won't come on until it's driven a short distance, I think because the coolant has to get a little warm first. if you have a bad thermostat and the coolant doesn't get up to temperature high enough to trigger the blower coming on, it may delay it coming on. This would account for the erratic behavior and also lack of enough heat. Hope this helps.

[macdrone]

His MB wont have that strip fuse unless he was retrofitted due to the service bulliten. For about 40 dollars in parts he can get it rerun like it should be. It was like a silent recall for popping the fuse inside the fuse box due to large power draw.

[throne7]

Make sure you takethe wiper arm / wiper off. Otherwise you can easily crack the windshield.