I have an 09 DTS with just the front climate control. The blower stopped working but when connected directly to the battery it turns on. I then tested the voltage of the wire connected to the blower motor, when disconnected it reads 14V when the car is running but as soon as it is reconnected to the blower it reads 0 at all fan speeds. So I went to Advance Auto and bought the resister pack but it did the same thing and does not power the fan. I used alligator clips with wire to a battery pack turned the AC on and then the battery pack and ice cold air. I just don't know where to go next since the fan works Any advise how to actually test the resistor or where to go next?

 

So the wires that go to the resistor are black, red w/black, and gray w/blue. When using a volt meter both red w/black and gray w/blue read full battery voltage regardless of hvac setting on or off and ignition on or off. Then there are 2 wires going from the resistor to the blower red w/green and black w/red. Same with this one red w/green reads battery voltage regardless of hvac settings and ignition on or off.

I have no clue what to do next, any ideas?

 

Blower is supposed to be pulse width modulated they normally don't work with contestant power and ground.the resistor/ blower control module should have 2 connectors and a total of 5 wires. 1 connector 2 wires blower purple modulated 12v to blower. Red/Black should have is ground circuit for motor. 2nd connector 3 wires black wire is ground / pink and orange wire 12v from fuse. grey/green goes to control head for fan command. What do you have on the different wires?

 

My wiring is different colors, one connector with three wires are black, red with black stripe (12 gauge) and gray with blue stripe (16-18 gauge) The other connector has two wires red with green stripe and black with red stripe both about 12 gauge.

When the car is on but not running and fan speed is off both leads going to the fan read 12.3 (red w/green and black w/red) Also the hot wire from the fuse red w/black reads 12.3 but the signal wire 18 gauge reads 12.2 and nothing changes when the fan is turned on high, all voltage stays the same.

If I shut the car off all wires are still hot and read a tenth higher. two leads going to the fan read 12.4 (red w/green and black w/red) same for the fuse wire and signal wire 12.4 for fuse lead and 12.3 signal wire.

I don't know why both sides of the fan read 12v, I also did a continuity test on the motor and for whatever reason the motor has continuity but again if I hook it up directly to 12 volt battery the motor spins without a problem

 

Both sides read the same because module is not grounding circuit. Ok lets do this.
with key off unplug 3 wire connector:

1) with ohm meter check black wire to ground should be less than 1.0 ohm . if not high resistance or open wire.

2) with key on using test light check red/black wire will it light? If not, check fuse and relay or there is high resistance on circuit. If there is voltage and it won't illuminate test light there is excessive resistance is reducing amperage not allowing blower module to work.

3) with key on Connect test light between gray/blue wire and black/red wire using control head see if blinks and blower speed is changed.
if light is always on - check control circuit for short to ground
if light is always out - check control circuit for short to voltage.
If control circuit is ok replace HVAC control head.

You actually want to test at terminal end of connector and be sure terminals aren't discolored or burn't. Post what you find

 

So I checked the ground and it is at .2 ohms with it set on 200. I then used the test light to red w/black and it lights up bright. I just don't know what you want me to do on the 3rd step a little confused. I should jump the signal wire and the red w/black and see if the light pulses?

When the 3 wire connection is removed from the resistor the signal wire has no voltage regardless of fan speed setting.

 

Connecting test light between battery feed and signal you are looking for a signal from control head (flash). The resistor is actually a module. The signal circuit is tied to the logic function of module. It's looking for a voltage change to turn on fan or change speeds.(flash)

 

Nothing happens when connected to feed and signal.

I removed the hvac controller from the dash and could not find a gray w\blue wire because I wanted to see if there is continuity, where does the gray w/blue wire run to bcm?

 

wire changes color at connector 202 to gray/pink it goes to pin 7 at A/C control head at dash.

 

So you think the Ac control head driver went bad? Replacing the HVAC control should fix the issue right? Is it weird all other function on the control head still works?