Intermittent heater blower operation in '70 280SEL

[M_Anker]

Hello,

My 1970 280SEL has a heater blower motor that it acting up. It's operation is intermittent, but when the fan operates it does turn smoothly. Does anyone know where the wiring harness at the fan motor is located and if this is a common problem?

Off topic, what it the going price for a Becker Europa radio, mono?

Thanks!

[300SDog]

German engineers designed the entire automobile around the heat blower motor, located at exact geographical center of the automobile buried behind the dashboard up against the firewall.

Mercedes legend and lore says that craftsmen assembling the finest sedans in the world started with heater motor and attached unibody frame, suspension, engine, drive train and finally the interior appointments all around this simple component.

Modern MB's from the early 1980's include automatic climate control....... an insanely complex system of sensors, relays and vacuum servo-switches that nobody can understand. On more primitive late 1950s and early '60s versions, heat blower motor was luxury addition that was bought as extra feature such as sunroof and AM/FM radio.

If it was me, I'd first check the dial switch that activates the heat blower motor...... then pray to god the fan motor itself does not ever need replacing.

[M_Anker]

Yeah, I've heard the stories about how MB hung the motor on a string and built the chassis around it. My service manual shows that there is a series of resistors somewhere around the fan, and that they come after the speed switch. Is there any way to reach the wiring harness leading into the motor housing itself? I think I most likely have a loose connection somewhere since I've been working on the radio recently.

I can get wonderful defrost up at interstate speeds, but that's mot going to do me much good this fall when I have to get up at 7 in the morning and go to school.

Also, I searched the archives here and soemone mentioned that there is a section about the blower motor in the 1960's vintage service manuals. Can anyone send me copies of these pages? I would be happy to reimbuse for postage, materials, and time.

My 1970 printing has all kinds of information about the air conditioner, but nothing about the heating. Calling the section "Heating and Cooling" is somewhat of a misnomer.

[M_Anker]

I found a few threads in the archives here that said you could gain limited access to the blower motor by removing the cowling. Well, after tracing all the connections last night and getting no where I decided to try this. I removed the cowling, and the blower motor was conveniently hiding beneath a nice piece of sheet metal. I was able to access it from the side, through that nice narrow passageway. First, I cleaned everything out with a vacuum cleaner and air hose, but there was little more than a few pine needles. I then found that the motor was turning freely, but it would not start without a nudge. I first cleaned all the contacts with a strong spray of electrical contact cleaner and got the fan running, somewhat. Then I sprayed the whole motor down with WD-40, and it spun up that time. WD-40 will clean anything, including dirty contact on a motor.

Thanks for making this forum available. That little trick with the cowling certainly wasn't in the MB service manual. You guys sure saved me a load of grief.

[martyg]

Can you be a little more specific about the cowling replacement. What is it? Where is it?
I have a 1985 300SD that is having the same problem you descrbed.

[dmorrison]

martyg

Our car is newer and set up differently. Remove your passenger knee panel that is above the passenger feet and under the right side dash. That is where your blower motor is located. It is common for the brushes on the blower motor to wear out and then it does not always start. You can replace the blower motor with our without the squirel cage, blower. Or buy and install the new brushes from Stu Ritter.

Do a search on blower motor brushes.

Dave