Heater Cores and Blower Fans

Why does your heater fan only run on high speed?

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2006-05-18 21:58:41
2006-05-18 21:58:41

99% of the time it is the heater resistor block, it is a bunch of resistors which gives you the different speeds. this is mounted close to the heater motor, pass side of the car. Usual cause of failure: water or snow inside the heater housing.

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Yes there is, but it only operates the high speed function.

Switch problem? Cables disconnected?

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.

Check the low speed relay and the resistor at the motor

now when you say replaced heater fan multi speed are talking the fan or the switch because ther is a fan speed resitor that can go bad and fan only works on high speed which can cause conector to get very hot and cause insolation on the wires to melt and cause a short in the harness making fan run constantly.

Check the resistor pack on the evaporator case under the hood

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,

I believe you have a relay that runs the high speed for the heater fan motor. The relay should be located in the power distribution box under the hood.

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?

it is usally a dry connection on the fan speed switch

If its the fan speed your talking about its likely that the speed controller on the fan is broken and had its days

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.

This is a very common problem. Most often the reason that a heater fan won't run on one of the speeds?æis corroded contacts in the wiring harness.

Most heater blaower motors have 2 relays: 1 for speeds 1-4 and a high speed fan relay for 5th speed I do not know what kind of vehicle or location of relays Most heater blaower motors have 2 relays: 1 for speeds 1-4 and a high speed fan relay for 5th speed I do not know what kind of vehicle or location of relays

If only high speed is effected check the high speed relay and/or the fan switch/electrical connections for problems.

The fan control module in the engine compartment has gone bad.

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.

I'm not a mechanic, but I do believe if you bypass the resister you will only have high speed on the fan. To that end, if the resister is your problem you should already have only high speed on the fan.


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