Odd effect of defroster on GPH

[3dplane]

Originally Posted by BurningDinosaurBones

Another theory here is that the speed control on the fan can be controlled by resistors in series with the fan motor. The resistors' job is to drop the voltage in the line to reduce the fan speed, and release the extra energy as heat into the heated air stream in the duct. Three resistors of a different resistance produce the three lower speeds and then when switched to maximum speed the fan has zero resistance in series with the fan motor and runs at it's designed speed and current (Amps), and it's maximum efficiency. This could account for your drop in current at the fans highest speed.

I like your thinking but the overall power required to run the fan full blast is higher (a lot) than through resistors. Even though it seems they just simply waste the rest of the energy in heat to slow the fan down.
BTW Welcome to EM!

I meant to tell Kodak: Please check your blower resistor connector (passenger front under dash)! It is very easily accessed,you just need a flashlight to see under there. On Canyons and H3s I see this problem all the time that the terminal in the blower connector has poor contact and heats up to the point where the plastic melts together into the terminal eventually blocking electrical contact (blower high will not work) and makes it impossible to unplug from the resistor assembly! It should be white connector and you look for discoloration around the wires or even the wires it self near the connector. Unplug it and look straight up into the resistor where it plugs in and look for signs of heating.

For your 07 truck the problem might be fixed by GM, OR they just have not included 07 model year in their bulletin yet. Searching as an 06 , the issue is there in service information (GM)
Barna