I have a 2002 Pontiac Montana and the blower motor works on all speeds except high. Is most probable problem the blower motor resistor? As an aside, the same time this happened my headlights failed to be bright any longer, whether on high beams or low beams, could this be a connected problem?
I have checked all fuses and all are fine. Have checked the battery and alternator, all
voltages are reading properly.
SOUNDS LIKE THE FAN SWITCH IS BAD THATS WHY IT DOSENT WORK ON HIGH
You are right on track. It could be either the fan switch or the resistor but my money would be on the resistor. Your lights are probably a separate issue and not related but fix the fan speed first and then see if the other problem goes away. Good luck.
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