QuestionQUESTION: I have a 1993 Chrysler Concorde. When it is either very hot or very cold, when I turn on the heater/defrost switch it will make a grinding noise for a few minutes and then stop. Sometimes it makes that noise as soon as I start the car. Sometimes it doesn't even make any noise. The fan always works. Is the switch bad and how do I replace it or is it something else? Thank you
ANSWER: Hi Casey,
The best way to identify the source of the noise is to move closer to the possible sources and use your spatial differentiation provided by you ears to identify if it is from the control unit where the switch is, or if it is coming from under the dash to right of center on the under side of the air distribution housing which is where the fan is located. Listen for whether the sound is a mechanical rubbing or grinding sound as opposed to a static-like sound which would suggest a problem with the switch or the electronic module that varies the voltage to make the fan run at different speeds. You can gain a better sight and sound view of the housing by removing the silencer duct on the right hand side of the lower edge of the dash.
Let me know if it seems to be coming from the blower housing as that can be taken apart to either replace the blower motor or adjust the blower wheel in case it is hitting the inside of its housing so as to produce the grinding sound. Motor bearings are usually fairly consistent in their noise level, while the blower wheel might rub or not rub depending upon flexing of the plastic housing which might be affected by temperature.
So let me know when you have a better idea of the source. The blower is in a round housing on the bottom of the right end of the unit. You can touch the housing to determing if the sound is caused by the internal spinning wheel is rubbing on it. Also tell me if the unit has a digital temperature readout or not as that may affect the nature of the repair.
Roland
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QUESTION: I will get back as soon as I can check out where the noise is coming from.
ANSWER: I'll be interested to know what you find.
Roland
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QUESTION: I was taking a really fast look for the housing unit. I am looking at a black metal cover that would be about where the passenger's feet would go and right about where the air comes from the heater on the passenger side of the front seat. The middle console gets in the way a bit. Is this the right place to find the silencer duct ? Also there is no digital temperature readout. I think you are on track that the hot/cold makes the plastic housing unit touch the fan blades. As I said before it doesn;t do it all the time so I have to more or less wait until it does it.
AnswerIf you can see the underside of the housing removing the silencer duct, that is all that is necessary. If the black cover has a twisted pair of wires coming from it that go to a nearby plug in the body of the housing then that is the lid of blower motor housing and blower fan wheel. You should feel some vibration when the blower is turned on when you touch it. The type of control you have is the conventional type, not the automatic type. This is probably a blessing. But in any case the control panel is probably not involved.
Roland
