Defective ballast resistor pack.OTHER :
It sounds like it could be the blower motor relay / resistor. I replaced mine today in my 2001 Chevy Impala. It was next to impossible since I heard that the way to get to the resistor was to remove the blower motor housing and repair it that way. I instead removed the blower motor and got to it that way. The two screws in the back are knuckle busters. Good luck and I hope you have patience or enough money to have someone else repair it.
try replacing the blower motor resistor
The blower motor speed resistor is burned out.
Check the low speed relay and the resistor at the motor
do you mean the speed of the fan? if so, it'a relay generaly near the motor of the fan. If it's the heat who only came at high speed, you need to add some antifreeze.
2004 Chevy express van, heater has no high speed, at one time the blower stayed on even when the ignoton was turned off therefor draining the battery,
blower motor resistor is burned out
you might need a new switch.
Defective heater resistor pack.
The blower motor resistor pack is bad.
The blower motor speed resistor is burned out. The high speed function bypasses the resistor. The speed resistor is generally located near to the blower motor.
If all speeds do not work, suspect the fuse, the switch, the switch connector or the blower motor. If only high speed works, suspect the blower motor speed resistor. If low speeds work and not high, suspect the blower motor relay.
Maybe because your climate control system needs to be repaired....
Your '92 Mazda 626LX car heater and AC might work on lower settings but cut out completely on full power because of a faulty rheostat. The fan speeds will not work correctly when this part is bad. Generally the high speed function bypass's the blower speed resistor. The high speed function uses a relay instead. I would start with checking the high speed blower relay.
If you mean the fan - replace the fan speed resistor if the fan only works on high speed. Please supply more information - no heat or cooling? Does fan work? Does mode switch work?
I have a 1990 Toyota Corolla and it did the same exact thing as yours and eventually only high speed would work and further investigation revealed the fan switch in the heater control assembly as the culprit. The contact points in the switch had all burned up except for the high setting so I went to the dealer and got a new one and no complaints yet. *********************************************** Jvrsshurricane is right, but more often the resistor is the culprit. High speed = no resistance, low speed = most resistance
If its the fan speed your talking about its likely that the speed controller on the fan is broken and had its days
The first thing that you need to check will be the coolant level..................
It means that when it only worked on high, that the resistor in the blower fan wiring went bad and the only speed the fan would run on would be a speed where NO resistor was being used, which is the high setting. Your fan went bad because it WAS only running on high for so long and now the entire assembly needs replaced. It's a PITA to get to because it's up in the dashboard so while you're in there, change out your heater core and wipe everything clean.
try replaceing the switch that controls the low to high for heater It's gonna be the blower motor resistor (near the blower motor).
Defective Heater Resistor Pack.
Most likely and bad blower motor resistor.
You most like have a bad blower motor resister.......
your heater resistor is on its way out ..some are built into the heater motor some on a separate board depending on the make and model of vehicle
toyotas have a resistor bank in line with heater motor each speed has a different value resistor. there is no resistor on high speed. it is located on passenger side in heater duct I thank it has two screws holding it on when you get it out you will see the resistors burned
12 speed, you mean 1 or 2 speed? Anyway, when a fan speed control only works on high it almost always means the Resistor Pack is defective and needs replacing. It can be the speed control itself but it is highly unlikely. 99% of the time it is the Resistor Pack.