Heater resistor the fan switch only works on 5

The Heater Fan has a Resistor Pack that Varies the 12 Volts (( 13.6 )) from the Battery to the Electric Fan Motor. The High Fan setting uses Full Voltage (( no resistance )) This could be the Fan Switch but I would suspect the Resistor Pack.

need to check switch,resistor and fan ---ur switch might have resistor built in it would need to be tested for continuity for the other speeds --if your truck [didnt specify which ] has a separate resistor it should be attached to the heater fan motor housing again resistor needs to be tested -also test ur fan for any resistance or overheating

More likely it's your fan speed switch. If the resistor pack goes bad, usually fan only works on high speed, but is still turned on and off by the fan switch. If yours stays on all time with key on, and won't turn off by the fan switch, probably a bad fan switch.
The resistor will be on the heater case, mounted with two small screws, a small rectangle with a wire connector with 4 or 5 wires to it, and not far from the blower motor.

Usually what happens is the switch goes bad and starts sending multiple current paths to the resistor. Then the resistor pack burns up as well. There is some detailed discussion on this at http://www.fixya.com/cars/t5072781-location_blower_motor_relay

The Blower Motor Resistor is located on the passenger side firewall, not far from your A/C's H-Valve (or expansion valve), going inside of the vehicle. The blower motor resistor has a 4 or 5 way black connector plugged into it and this is the only visible portion of the Resistor you will see. Remove the wiring connector and remove the 2 or 3 screws with an 8 mm or 5/16" socket (8 mm and 5/16" are the same). Once the screws or fasteners are removed, just pull the blower motor resistor out of the firewall and if you look at it, it will have various coils of wire on it, sometimes it will show burnt coils, but you can always check the various coils with an Ohm-meter.

Aside from that, install the new Blower Motor Resistor and Voilà! Your inside Blower Motor should work just fine.

A brief note here, if your fan doesn't work when the fan switch is on High, then it's not the Blower Motor Resistor, but possibly the Blower Motor itself. Should this occur, please get back to me insofar as how to replace the blower motor and why the blower motor's wires have to be twisted...even with the new blower motor fan.

Best of Luck,

"00 Buck"

"Still living on the Right Side of Dirt..."

Underneath the glove compartment on the passenger side is a cover which must come off,2 plastic screws holding this cover.Underneath you will find a 5 pin connector[big plug] connected to a white connector in the blower fan housing.This is called the fan resistor which controls the blower fan speed.Unclip the resistor out the housing and renew.Your problems should be solved..regards

it is must likely your fan control model -it control's
the fan speed location of model is next to blower

The fan resistor is under the right side of the dash at the bottom of the heater case. on this car they generally fail because of a water leak into the heater case. The leak will have to be found and fixed, or you will burn another resistor out if you replace it.

blower motor or resistor or the blower motor control switch.

When your heater only works on high it is usually
the resistor unit in the heater passage housing. Look for wires ( about 4or 5 wires ) attached to the
plastic heater housing under the dash. It should
have a screw or two holding it to the housing. Pull
it out and you will see several wire coils. If they are melted or broken then thats the problem. On any switch position except high the power goes through these resistors to slow the fan down. Good luck. Neil W.