QuestionQUESTION: Hi - my 300M (121,000 miles) has an automatic setting on the environmentals. Lately when it's on automatic, the defrost setting seems to be a lot (even in nice daytime weather) and there is a high pitched whine which stops if I hit any button (which also takes it out of automatic mode).
If I just turn on the heat manually, I never get the whine. When I turn the defrost on manually, I don't seem to get it. When it's on automatic, I get the whine sporadically. It seems to get louder as the engine RPMs increase, then decreases when the transaxle shifts.
But I also get it when cruising down the freeway at 65 MPH (that's where we first heard it and noticed the defroster was on when we didn't think it should be.)
My dealer's service manager looked at it, heard the noise for a minute, but couldn't isolate it before it stopped. He's a good guy, and hasn't even charged me for trying to find the problem.
Any ideas?
ANSWER: Hi Kevin,
I don't know what the sound is either, but it would be worth running the self-diagnostic test program for the ATC. With the engine running and the temp setting at '75>SNO f', simultaneously press the right three buttons on the control panel (floor, mix, defrost) which starts the diagnositics. The lights will blink for awhile. If there are no noticed faults the reading will return to normal. Otherwise a two digit code number will appear. Press the 'panel' button to see whether there is another code number, etc. After you have done the readout, write back with a follow-up question and tell me what the number(s) are.
Roland
---------- FOLLOW-UP ----------
QUESTION: I tried what you suggested, but nothing happeded. I set the temp to 75, then pressed the lower case last 3 keys (floor, mix, rear defrost) - nothing. Then I tried upper case (upper heat, front defrost-floor heat, front defrost) - still nothing. Panel still showed 75. Changed temp to 76 and did the same things - nothing.
Did I do something incorrectly?
ANSWER: Hi Kevin,
I now see the upper/lower case possibilities. So do it lower, upper, upper on those three buttons, simultaneously, with the engine running, and hold them in until the display starts blinking. Then see if that starts the diagnosis which takes nearly a minute. Sorry to have been not so clear, the manual doesn't clearly distinguish that each button has an upper and lower choice. Just says "floor,mix, defrost", but the drawing appears to indicate lower, upper, upper, left to right on the the right three buttons.
Roland
---------- FOLLOW-UP ----------
QUESTION: I ran the diagnostic, the numbers flashed for a minute, then went back to 75 (the temperature setting). I also did more playing around - the whine is definitely there only when the defroster is on, sometimes on auto, sometimes on manual. Turn off defroster, noise stops. Dealer service guy said he thought it could be a door with an electric motor? Does that make sense? Would it be going bad (noise is intermitant, not constant)?
Thanks for your help.
AnswerHi Kevin,
I suppose it could be a door actuator motor but the self-test would probably be able to detect that. The defrost is a position where the air for the windshield is deflected to pass over the a/c evaporator core. I am not really in a position to offer any further advice. I am glad that you did do the readout successfully. Maybe it will resolve itself spontaneously, or you can keep checking the self diagnostic mode once in a while.
Roland
