Evening all, my blower has stopped working period. New motor, resistor and control panel, still nothing. I have checked all of the listed fuses, is there something I’m missing? I can’t for the life of me figure out what else it could be! Any help is appreciated

 

Below is a condensed wiring diagram, note there are effectively 5 wires connected to the Blower Resistor ( GM call it a "Blower Control Processor") BLK & RED are the "Tails" going to the motor and A,B,C are the HVAC connector pins.


Follow these steps:-

1. Check there's +12V across pins A + C. If so go to step 2, if not check:
   • Pin A connects to both GND G203 and the H2 chassis.
     
   • Check there’s +12V between chassis and Pin C, if not check the 40A Blower Fuse and/or inspect the underhood fuse block.
     
2. Check there's +12V across Pin A (GND) and the Red wire going to the motor. If so go to step 3. If not disconnect the resistor module and measure between Pin C (+12V) and the Red wire on the module itself, there should be zero Ohms as they're connected together internally, if not it means the resistor module has probably burnt-out and gone open circuit inside.
3. Measure the DC voltage across Pin A (GND) and Pin B (Speed Ctrl) [note this is a Pulse Width Modulated signal (PWM) and not a pure DC voltage] Turn the A/C ON and set the Fan Speed to zero, the voltage should now read approx +5V, increase the fan speed and observe the voltage drops as speed increases, the lowest value being around 2.5V. If this is OK the HVAC control module is working correctly so go to step4, if not either the output of the HVAC connector C2 Pin M is disconnected, or either the HVAC Control Module or Resistor Module are faulty.
4. At this point the only remaining options are the Blower Motor or Resistor Module. If the blower motor has continuity i.e. < 2 ohms then its most likely to be the Resistor Module.

These tests are pretty quick and easy to do, feel free to ask more questions, happy to help

 

Did you put the new motor and resistor in at the same time? If you put the resistor in first, then turned it on, the old motor could have fried the new resistor.

 

... good call.

You can test the fan by connecting it to 12V however it needs to be secured due to it's inertia (trust me) it also draws a lot of current (around 15A) so it is quite scary (but that is what it does in vehicle)

A lower voltage would be better if available, for reference at 5V the fan pulls 5 Amps, so 12V will be around 12 Amps

Here's a graph of the resistor control voltage range.

When the Resistor Module fails it's MOSFET power chip often goes short-circuit, so the motor is literally connected across the battery and just keeps going, of course the 40A fuse never blows

[Awaiting Resolution]

 

I didn't think about that, i only had it on for a few seconds to test, but yeah i guess it could have blown the new resistor right away. They blower was locked up when i removed it. ****. But i will be doing a voltage test before i just buy a new one. These things suck, they only last about a year...

 

Yeah the constant running is usually what i got when the resistor blows, but this one is doing nothing at all.

 

coffeydp the circuit diagram below represents how the blower module is wired internally.

Q1 is a MOSFET transistor and typically when this "fails" it goes short-circuit internally i.e. pins 2 and 3 connect together. Thus the motor ends-up being permanently connected between +12V and 0V and so keeps going, however the motor itself is fine.

If the motor's seized it will cause abnormally large currents to flow through Q1 thus destroying it completely, so it appears like nothing works.

 

May be possible to repair your Blower Resistor

 

Unfortunately I don’t have the skills to follow all that, or the original one. I have had to replace that thing like 3 times.