QuestionQUESTION: The lower fan speeds, 1 thru 3 work, but when you switch it to 4, Hi Speed, it will NOT. Sometimes it will blow the fuse. I replaced the resistor to get the 3 lower speeds to work. I have also installed a new blower motor because the original was dragging too much. I understand the hi speed gets its power directly.
ANSWER: Bill,
I do not have diagram for that year but I believe this info may be similar.
The power for position 4 is routed totally different from the other 3 positions. The first 3 positions go to the motor via the resistors. Position 4 kicks the A/C relay which then routes voltage to the motor via it's N/O contacts, bypassing the resistor pack. Therefore I would check or replace the A/C relay. Otherwise, there is likely a short to ground in the relay circuit. This theory would be further confirmed if the fuse you found blown is the A/C fuse, instead of the fan fuse.
- Rick
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QUESTION: Thanks Rick,
Here is some more info.
The A/C works on the lower 3 fan settings. Sometimes when you switch it to the HI speed it will blow a 30 amp fuse which controls ALL 4 fan speeds. Do you still suspect the A/C relay?
ANSWER: Bill, The 30amp fuse should be for the A/C circuit. I would try just pulling the relay for testing purposes; I would think you'll get no fan but also no blown fuses in position 4. The problem may actually be the A/C compressor or it's circuits. Let me know what happens after pulling the relay, I have some ideas after that.
- Rick
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QUESTION: Rick,
I tried pulling the relay with the A/C on and off. Still no fan in #4 position and I still had ALL the lower 3 fan speeds whether the relay was in or out.
AnswerBill,
I believe you have made progress, it seems to be down to the A/C circuit. If my diagrams are correct for '91 (mine are '89) position "4" kicks the relay, which also sends voltage to the compressor only if the A/C button is pushed. I would reinstall the relay, then making sure the A/C switch on the dash is OFF, then try the fan again in all positions. If everything is fine, then it is likely the A/C compressor. Try disconnecting the control wire at the compressor (under the hood), then turn the A/C switch ON and try everything again. If all is fine, the compressor clutch is bad.
Rick
