Location of Heater resistor, possible problem? - Mercedes-Benz Forum

 
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post #1 of 7 (permalink) Old 10-28-2012, 09:38 AM Thread Starter
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Location of Heater resistor, possible problem?

The three speed fan switch is not turning on the blower motor. I have hooked up a direct power supply to the blower motor and it gets up to speed and seems to have no issues. I hooked up a multi meter to the wiring that is coming into the hub in the dash that has the levers and cables and it showed no signs of power coming from any combination on the six pins. I have replaced all the fuses that I could find under the hood. Could it be the heater resistor? Where is its location and any ideas and suggestions of what I should check next? The car is a 1972 250/8. Thanks guys!
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post #2 of 7 (permalink) Old 10-29-2012, 04:48 AM
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Check the change over switch. It is a micro-switch mounted on a bracket on the center console just above the accelerator pedal (LHD cars). This switches the power from the A/C recirculating fan motor to the actual heat/defrost fan. Pretty common for the rivets on the bracket to come loose and not allow the switch to engage.
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post #3 of 7 (permalink) Old 10-30-2012, 01:05 AM Thread Starter
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checked the micro swith, and it seems like its working. I'm still having an issue with no blower motor getting any power, so I continue to look for the solution.
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post #4 of 7 (permalink) Old 10-30-2012, 12:43 PM
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Do you have a wiring diagram? There's one posted to the online resources section of the forum, I believe...
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post #5 of 7 (permalink) Old 11-01-2012, 08:05 PM Thread Starter
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PROBLEM SOLVED!!!

Ok.... So don't think I'm an idiot. So all I wanted was some heat in this thing for the winter thats coming up. The whole time I was testing the blower motor I was testing the air conditioning blower motor that is sitting at the bottom of the consol. After learning that there is a seprate heater motor that is just under the outside center intake, I began to remove the dash. What a pain in the A$$! Well, it turns out that the motor was completly seized because of years of dirt that had been blowing into it for the many years that this 250 was just sitting around. I was able to unseize the motor and spray some electric motor cleaner into the motor. Hooked up all the wiring again turned the switch and the motor starting spinning like mad! So after about two hours of trying to get the dash back in (which was harder then removing it) all seems to be well! The project continues.
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post #6 of 7 (permalink) Old 11-02-2012, 08:53 AM
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Only two hours to get the dash apart? I salute your efficiency and speed! I did the one in my 108 and it took about 30 hours total to undo and reconstruct!
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post #7 of 7 (permalink) Old 11-28-2012, 11:48 PM
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Question Change over switch

Does anyone know of a place that has a new change over switch or knows how to fix the old one?? Mine doesn't work. The mechanic keeps jumping the switch to make it work for heat or A/C. Any ideas everyone??
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