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Car Forum / Mercedes-Benz Cars / May 2005Help Needed With 1985 300SD Diagnosis
Here's the scenario One morning my Ac/heater fan (blower motor) would not start. Checked out and found blown fuse to blower motor. Today I started out to the same situation , but when I went to replace the fuse it wasn't blown. So this is my delimma. What do I check next? Set the fan speed to high... with engine running and all... hit the passenger side lower dash. If the fan comes on... you need to replace the fan motor. Tried striking passenger side with no results / Also I don't think I( have an auxillary pump on my car. What to check next? Or just assume the blower motor is bad?--NW >Set the fan speed to high... with engine running and all... hit the >passenger side lower dash. If the fan comes on... you need to replace the >fan motor. Check the fuse first... take it out and check it... If you never changed your fan motor... it is most likely shot. However, there is another device that controls the motor too... My advice is to take the cover out and check the voltage at the fan harness... if 12V or higher, then motor bad. The other thing that controls the fan is called resistor pack. Checked out the fan motor this morning . It's not getting power. removed it and tested it . It works fine. Where is the resistor bank?--K Checked out the fan motor this morning . It's not getting power. removed it and tested it . It works fine. Where is the resistor pack?--NW Ask TG directly. > Ask TG directly. As I recall there is a resistor housing on the right fender well under the hood that controls the fan speed. I'll check further tomorrow and let you know. Now that I think about it there may be a similar device on the driver's side firewall as well. Dang....age must be gettin' to me. If your model has an auxiliary (electric) water pump to supply the heater, it may be worthwhile to disconnect it's power cord, if only to exclude it from the possibilities. The pump in my car was shorted (by coolant) and blew two fuses, causing the blower to quit. The heater pump runs only for a relatively short time so the heater's performance is hardly affected by its being unpowered. >If your model has an auxiliary (electric) water pump to supply the >heater, it may be worthwhile to disconnect it's power cord, if only to [quoted text clipped - 5 lines] >The heater pump runs only for a relatively short time so the heater's >performance is hardly affected by its being unpowered. Ok here's what I know ( or think I know) No blown fuses No power to blower fan supply I have searched and I do not have an aux. heater pump there apears to be a straight pipe to the firewall fuses 10 and 11 were blown at the start but not since it died I suspect the ignition switch Am I on the right track or what else do I need to check?--NW Also checked voltage going to blower regulator Have voltage on red/yellow going in . Could this be the culprit?--nw For years I thought I was driving a 1985 Mercedes 300SD but after reading several descriptions of items to check that I can't seem to locate on my car , I'm not sure anymore. I have no auxillary water pump , I have no resistor pack to speak of . and one description of a silver box with holes in it I did locate but it is under the brake booster. Virtually untouchable. So if you can help please be precise in where to look for possible causes for my problem. Thank You --nw >Also checked voltage going to blower regulator >Have voltage on red/yellow going in . >Could this be the culprit?--nw Write a new post... it is possible that TG just missed those old one... write new one so you are on the top... or write to him directly. |
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