There could be several reasons, but the most common when the fan works on high, but none of the other speeds is that there has been a failure in the fan speed control RESISTOR PACK. At the high speed setting, the 12 volt vehicle supply is fed directly to the fan motor. On all the other speed settings the voltage is proportionally reduced by the series combining of heavy wire resistors. The resistor package is inserted into a rectangular opening in the blower plenum chamber [encloses the heater core, and the air conditoner evaporator coil]. Depending on the vehicle, it may be on the passenger or the engine compartment side of the firewall/cowl. It is normally secured in place with two to four screws, and the wiring harness is connected to the pack with a plug on connector. j3h.
there is a resistor that controls the speed and should be near the blower motor its called blower motor resistor
i have a 1998 buick century and my blower motor is under the passenger side front wall inside.I found out that the blower motor resister was the problem.if it works on high speed only,replace the resistor first.it's cheaper but harder to get at.
Check the blower resister
Either than switch, the resistor, or the relay is bad. On my 1999 Buick Century, the blower motor quit working on the three lower speeds, and then went out completely. When the resistor goes bad, the lower speeds quit working. My blower motor was squealing, also. After I replaced the blower motor and the resistor, I tested it and found the blower worked great on every speed but high. It turned out that there is a separate circuit for high speed, and the fuse was blown. I replaced the fuse for the high speed, and the blower now works on all 5 speeds. Replacing the blower and resistor was difficult, but not as bad as expected, thanks to help from this site.
either your blower is bad, or you need a a/c recharge.
the blower switch itself is located in the instrument panel. it adjust the speed of the blower. the blower resistor, if that is what you are looking for,is located beside the blower motor under the pass. side of the dash
If you are referring to the blower motor only working on the high speed setting, then the problem is the blower motor Resistor Pack is defective. Replace it. It can be the blower motor speed control switch but not likely.
my 1999 winstar was doing this and it was the blend door
under dash on pasenger side
Sounds like it could be the actaul switch that's used to select the speeds. ADDITIONNAL INFO SEE DISCUSSION PAGE.
If you are saying the blower motor only works on the high speed setting, then the problem is a bad HVAC Resistor Pack.
The blower motor relay for high speed would be located in the power distribution box under the hood.