Chrysler Repair: Concorde98 blower problem, wire colors, chrysler dealer

Question
In my '98 Concorde AC blower sudently start working on high speed. Knob to adjust blower fan speed is
not responding. Even if I turn all system off, the blower never stop. I have cold and hot air, I have all distribution vent working, the only problem is that I can't adjust or stop blower fan. Last week I removed blower fan fuse because of noise. Local Chrysler dealer told me without checking that is car computer problem and estimate cost of repair between $600-$700.
Roland, help! Thank you.

Answer
Hi Anthony,
The dealer is 'blowing smoke'. That symptom is absolutely diagnostic of only one thing: the resistor block in the heater/AC air housing in the cabin has gone bad. This replaceable electrical component is what gives the variable fan speeds and when it burns out the only speed that works is high.
Begin by removing the right side under dash panel (below the glove box, gently pull down; when reinstalling make sure the left hand end fits into its ducting). If you look at the lower surface of the right end of the unit (where the blower motor is located) you should find a 4-wire plug attached to a rectangular plate held in place by two screws and the hidden part of the device will be positioned so as to have air blown over it by the blower (to cool it off so it can dissipate electrical resistive heat without burning out; the wire colors should be black/tan, light blue, light green, and tan). Remove the screws and take out the block. Then buy a new one at the parts counter or get one from a pull-it-yourself wrecking yard and save yourself $600.
Roland