Chrysler Repair: 90 New Yorker ATC Blower Motor overloads circuit, amp fuse, gauge wires

Question
QUESTION: I have a '90 New Yorker and as the speed of the blower motor is increased, you can see the battery gauge go down and the underside of the ignition gets hot. It has gotten so hot that the plastic housing has cracked and melted in a spot. I have had to replace the ignition switch several times. I have also had to splice a new wiring harness to the switch since a contact was very well burned. This happens whether you're running A/C or not. My question is : Do I have a bad blower motor or bad wiring? This car has the Automatic Temp Control. Thanks in advance for looking at this. - Dennis

ANSWER: Hi Dennis,
Yes, that seems reasonable, with a caveat:
The blower motor fuse is a 30 amp (powered by a 50 amp under the hood which itself supplies fuses 9,10,11 thru the ignition switch) and you may be close to blowing one of those. The current goes thru a section of the ignition switch powered by the pink trace wire from the 50 amp fuse and then on to the three fuses listed above. I would suspect bad wiring, such as a short, would frankly blow fuse #10. So long as any new wires that you installed were the same gauge as the original they should not be overheating.
That pretty much leaves the blower motor; however, the blower speed is modulated by the ATC power module, so it could be its solid-state components are overdrawing on their own. Maybe the best test to do would be to run the blower at high, by by-passing the ATC power module control circuit, and note whether the draw down/overheating is still present. You could safely do that by unplugging the 2-wire connector at the motor and then jumping between the disconnected dark green wires (which will have 12V on then when the ignition is "on" coming directly from fuse #10) and then ground the black wire (the other wire on the motor side of the disconnected plug). Use heavy gauge wires similar to what is there already. Then observe the heat/gauge reading for any change. If none, then the motor is bad, if the problem is gone then the ATC variable voltage circuit is bad.
Roland


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QUESTION: Where would I find the blower motor on this vehicle and what would the procedure be to get at it? Thanks for your help! - Dennis

Answer
Hi Dennis,
Unfortunately the manual doesn't show the motor, but I suspect that if you look under the dash on the passenger side, perhaps removing any padding that is on the lower edge of the dash for better access, that you can run the blower and locate it by sound. It will also be the case that there will be one lead with two wires whose colors I listed, that will go to the blower from the large trapezoidal unit that is on the right hand front of the box which is called the power vacuum module. It might even be in that module. But I suspect that sound will clue you in to its location.
Roland