The auxillary radiator fans on my 300SD
come on after the car warms up and stay on as long as the car is running. They shut down as soon as I turn the engine off. The tempurature gauge reads a little above 80 and, in one case, last night the outside tempurature was 58 degrees. A review of the posting indicate that a sensor on the engine may be the problem. If so, where would it be and I can I check it? BTW, I have 149k on the car. ------------------ Ralph Burnette 1993 300SD |
Ralph, this is probably the problem with the limp mode as well.
I would have the blue sensor replaced then recheck. Also, the auxillary fan relays have been known to stick and run a battery flat. Have this repaired soon, it is causing stress on the charging system. ------------------ Benzmac: Donnie Drummonds 300E ASE CERTIFIED MASTER AUTO TECHNICIAN MERCEDES SPECIALIST 8 YRS PARTNER IN MERCEDESSHOP.COM OWNER OF MB AUTOWERKS .COM |
First, thanks for the advise.
Second, I did some additional testing: I drove it to work this morning (almost 1.5 hours) and no problem with the fans. I drove home this evening and the fans were blowing when I pulled into the garage. I shut down the car which shut the fans down and then I turned the ignition on. The fans stayed off. I two diagnostic procedures for the w140: 1) Read sensors: a. set the tempurature wheels to the white area. b. turn the ignition key on (don't start car) c. press left and right auto buttons. d. wait at least 20 seconds and then press "REST" for at least 5 seconds. e. A number (1) will appear in the left window and a tempature or message in the right window. Push the "AUTO" button to proceed to the next reading: 1 - in cabin temperature (B10/4) 2 - outside temperature sensor (B10/5) 3 - left heater core temp. sensor (B10/2) 4 - Right heater core temp. sensor (B10/3) 5 - Evaporator temp. sensor (B10/?) 6 - ECT sensor (A/C) (B10/8) Will return "HI" for a short or "LO" for an open. 7 - Refrig. pressure in bar 8 - blower motor voltage (8 min - 60 max) 9 - Software status 10- Left rear heater core sensor (B10/9) 11- Right rear heater core sensor(B10/10) 12- Rear evaporator temp. sensor(B10/11) 13- Software status 16- Control App. for Active Charcoal (yes=1, no=0) With this test, everything returned normal. However, with this procedure, I got a E0 41 code - short in ECT: Procedure to check for error codes in memory: a. left temp. selector wheel to red b. right temp. selector wheel to blue c. turn ignition key on. d. press "AUTO" e. within 20 seconds, press both "REST" and "0" (at the same time) and hold them down for at least 2 seconds. f. the display will show permanent DTC codes. press "AUTO" to check next one: LEFT DISPLAY RIGHT E0 41 indicating a short in the ECT sensor. So, I think that the ECT is starting to go. Do you concur? In any case, I am checking the pricing of a replacement. If it is not too much, I will just get it and replace it. BTW, the above procedures saved me a lot of work. Thanks again! ------------------ Ralph Burnette 1993 300SD |
I think that I found it. I have two
sensors on the inlet to the thermostat. One has a single pole and the other has a blue top with two poles. I assume that you mean to replace THIS one (that is, the one with the blue top and the two poles). Do you suggest putting anything on the threads when replacing it? BTW, in the meantime, my alternator went on while I was on the highway. Thanks. ------------------ Ralph Burnette 1993 300SD |
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