Usually the resistor is located in the switch. If the switch is fine, then it can only be wiring or fuse. The fuse can sometimes blow leaving only one setting. Is the air con working properly, because a frind of mine had a wagon that also had this problem and he had his air con not working for some time. He got it re gassed, and the minute it worked, all the internal fans settings worked again. So could be something co dependant on power to that part of your switch. Good luck, hope it helps.
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The blower motor resistor is located within a foot of the blower motor in the duct that the blower motor blows into. The resistor is actually cooled off by the blower motor blowing across it. It has a wire harness that connects it to motor & fan switch. It is held in place by 2-4 retaining screws. Disconnect wire harness,unscrew retaining screws then lift out. Reverse order to install.
the blower motor resistor relay are bad about shorting out and melting the connector causing a loose connection and when you hit it or a bump it'll make connection and work. look under the passenger side dash and you'll see two wires coming from the blower motor. trace those two wires to a little black box with somemore wires pluged into it and try to unplug the other connector that has about five wires coming from it. turn your key on and your a/c with the blower speed set on high, try moving those five wires if the fan blows and quits, then this is the problem. you'll have to replace the resistor and the wire connector.
The switch or the wire harness at the blower motor has gone bad. The highest setting 5 has no resistor, so the blower runs on high but the high current flow ends up burning up the switch's contact on that setting or the resistor wire harness at the blower motor has gone bad. Common would be the switch it self, if the switch is good. Then it's going to be the wire leads at the speed resistor by the blower motor under the glove box by the passenger leg compartment. Keep me posted, be glad to help you get your Sierra running 100% again soon.
The GM trucks do not use vacuum to operate the HVAC system. Check for power at the purple wire at the blower motor. If you have power and the blower motor is still inop, replace the blower motor. If you have no power, check the relays and resistor behind the glove box. Four screws hold the glove box in place.
Most likely cause is the blower motor resistor. If you remove the glove box (4 screws, two on each side), the resistor is located behind the 4 relays. Two screws hold it in place. rmeove screws and pull it up and out of the HVAC case.
Start at the relay for the heater/ac making sure it is working. Remove relay and clean it off then replace making sure there is current through to the other side.Use a test light. from there you can go to the blower motor wiring.Under your dashboard. Look for the resistor which is a switch type gadget in between the battery current and the blower. Check to see if there is current passing through to the wiring before getting to the resistor.Replace if nessesary.
there is a small electronic controller located in the heater core exterior, on gm's these go out, If you handy with a solder gun, generally it will be a burned lan on the circuit board, these put out quite a bit of heat, that is why it is mounter near the blower.
does anyone know what the problem is???? 1998 GMC Sierra blower motor problem.... when fan is turned on it works fine then all of a sudden it makes a loud screeching noise and sounds like its gonna blow up, does it on all speeds. please help
Your blower moter is under your glovebox and very easy to replace.I dont think thats your ploblem.I would pull off the dash.It will snap right off without breaking anything.Then pull out the part that holds the selector switch for the fan speed.Then you unplug that switch.Clean the copper contacts.Plug it back in.If everything works again like it should and did in my truck then it is either that switch that is bad or the wiring harness.I would replace that switch.