Blower motor does not run on high

After checking your fuses, check if you get 12 Volts to the blower motor, if not check if there is 12 Volt at the resistor.

yes, many times it will run on high, as the high setting is 12 volts and doesn't not need a resistor. If you have more questions, please let me know.

It's common for the blower motor speed resistor and harness to melt causing your blower to only work on high and check the blower motor relay. The relay may have melted also causing the 12 Volt power to still be supplied even though the vehicle has been shut off. Good luck and you can but the parts needed at most Auto Parts store like Auto Zone, but i believe the GM parts department has the resistor and wire harness kit to ensure all the parts that may have been damaged due to the heat built up by the current used to run the blower motor on hi. Good luck and keep me posted, be glad to know you have your truck running 100%

if it doesn't run at all then the problem is likely the motor, if it has only high speed then the resistor is defective, but I have seen the resistor cause an inop blower at any speed on this car, so test the blower 1st by jumping 12 volts to the motor connector on the underside of the passenger dash.

Cadillac 1999 DeVille
If the front blower motor is not running with battery level power to it, you may have bad blower resistors which controls the speed of the motor.. Unfortunately the resistors are built-in the motor. You may have to replace the motor. If you remove the motor, you can recheck it by direct wiring power to it. OR you may have loose wires.
Also check the Heater and A/C Programmer module.

Here's some info I found from another posting.

Red is positive 12 volts coming from fuse of circuit breaker. The black wire is either the ground or the main hot wire going to the blower motor (3 pin connection only), and the gray wire (if is is small in size) is a variable voltage coming from the body control module requesting speed for the blower motor.The blower control module varies voltage on the main wire going to the blower motor, supposedly in accordance with the requested voltage from the body control module. Usually if all fuses are okay and present on the apprpriate wire of the blower control module, the a blower motor that will not run or stays running after the key is turned off is the fault of the blower control module. If the blower control module has failed the the cause must be determined (over amping blower motor) or else new blower control module may fail when powered up.Usually blower control modules have more than three wires. Usual connections are: B+ (battery voltage) GND (chassis or engine ground), two large wires going directly to blower motor (can be any color, but are usually 10 guage in size), and an optional wire that reports voltage level back to the body control module.

These motors use three separate sets of blower motor windings which Low, Medium, and High. The chances are that the selector switch is ok and the High winding or set on the blower motor is not good.

I do not know the color coding of the motor to be able to put 12 volts on one of the windings of the motor to try and force the high to make sure it is actually getting to the motor.

The only way to be certain is to get to the Speed Selector switch and try and find out if 12 volts is being selected to the high side of the switch that goes to the motor. You will have to take the dash apart, which is easier prob. better than replacing the motor which is in the firewall. You might be able to replace it from the engine compartment at a autowrecker, but the high may be a problem Chevy had.
So if you figure out the color of the wire that is the 12 V high, then with the car on and in the high position, apply 12 directly at the motor by exposing part of the wire with a razor blade or a poke through with a sharp tool just to see if it comes on.
Temp solution - Assume the motor is good and the switch may be bad, Remove the medium speed wire and swap it with the High wire and see if it runs on high. Then you will have Low and High ONLY.

There is allot there good luck!

E

red black and gray are just half the connections. Red is positive 12 volts coming from fuse of circuit breaker. The black wire is either the ground or the main hot wire going to the blower motor (3 pin connection only), and the gray wire (if is is small in size) is a variable voltage coming from the body control module requesting speed for the blower motor.The blower control module varies voltage on the main wire going to the blower motor, supposedly in accordance with the requested voltage from the body control module. Usually if all fuses are okay and present on the apprpriate wire of the blower control module, the a blower motor that will not run or stays running after the key is turned off is the fault of the blower control module. If the blower control module has failed the the cause must be determined (over amping blower motor) or else new blower control module may fail when powered up.Usually blower control modules have more than three wires. Usual connections are: B+ (battery voltage) GND (chassis or engine ground), two large wires going directly to blower motor (can be any color, but are usually 10 guage in size), and an optional wire that reports voltage level back to the body control module.

jump 12 volts to the blower motor connector and see if it runs, if it does replace te blower motor speed control module

Replace your resistor if you haven't already. I had the same issue with mine, it only worked on high.

trace the two wires by analyzing which power are you missing...

run a wire from the positive of the battery and put the red wire of the volt meter to it and place the black wire of the meter to the black that goes to the motor.

if there is 12 volts, you have a negative terminal to the motor.

if you dont have, then you dont have the negative terminal to the motor.

next transfer the wire from the positive terminal of the battery to the negative terminal of the battery.

now put the bllack wire of the meter to the wire and test the red /or blue wire that goes to the motor.

it should have a reading of 12 volts.

if there is no reading , then there is no positive 12 volt present on the blue/red wire.

from these test, you can know which wire does not have the power.

that is what you are missing..

tnx 4 using fixya,

cheers,

drcool


p.s.

you could have just missed the black wire to be screwed on the housing of the blower motor.