Blower motor not working, replaced module, still nothing...

Appreciate the ideas here. My 2005 Tahoe LT blower fan is not working on any speed. This truck has had the module replaced on 2 separate occasions. Last night I installed a new AC Delco module #15-81773 and its harness. The harness has already been replaced in the past and looks like new, but I proceeded to replace anyway after I plugged in the new module and got nothing.
The 40 amp Blower fuse and 10 amp HVAC fuse are fine. I also tested the fan with a 12v motorcycle battery and it spun up just fine with no bearing noise.

I am lost on a fix here, and my feet are freezing by the time I get to work. ...Help please! Thanks.

The only fuses I checked were the ones under the hood...not sure exactly what the fuses in the drivers side panel do as compared to those under the hood, but will check tonight. The climate control panel and the blenders seem to operate fine, just no blower..

Update - In the drivers side fuse box, I found the 10amp HVAC! fuse port to have power, but no power to the 30amp HTR A/C port. Visual inspected the wiring going into the 30amp port on the back of the fuse block and did not find any damage (burnt or broken).
At a real loss hear and it is going to snow tonight...Ugh.

I tried a another new resistor module and still nothing.

I was able to borrow my friends new Ethos Tech Snap-On scanner, which is loaded with GM software. It acknowledged the Tahoe quickly with little optional input required. I am not skilled at using the device, but I think I was able to use some of the basics. I ran the code scanner and came up with 7 codes related to
HVAC:
B0159 - outside air temp sensor circuit range/performance
B0164 - passenger compartment temp sensor 1 circuit range/perf
B0174 - output air temp sensor 1 circuit range/perf
B0179 - output air temp sensor 2 circuit range/perf
B0229 - Re-circulation position feedback circuit range/perf
B0510 - Output air temp sensor 3 circuit range/perf
B0515 - Output air temp sensor 4 circuit range/perf

I did try to clear the codes and I guess they came back, In addition, I did a functional test on the blower motor. The function test allows you to confirm if the buttons on the HVAC headunit send a signal. All the buttons were tested and confirmed to be sending a signal. The scanner doesn't tell you what the signal is (voltage/amp) just a on/off confirmation. Again, all buttons appeared to be operable. Oh, I did test the Blower Motor PWM Speed % where I could see from 6% to 78% with intervals in between. 6% representing the lowest blower setting and 78% being the highest. Well that's as far as I got with the scanner, maybe there are other tests I can do with it??

Does anyone have ideas on what to do next? Thanks!!

I got to where you were with my 05 Escalade...threw in the towel and replaced the blower...problem solved.

Wow. I am thinking the control module (head unit), but it never acted funky. I did test the blower with a motorcycle battery and it worked just fine.

Yukon John said:

I got to where you were with my 05 Escalade...threw in the towel and replaced the blower...problem solved.

Click to expand...

Wow. I am thinking the control module (head unit), but it never acted funky. I did test the blower with a motorcycle battery and it worked just fine.

Johnb21 said:

Wow. I am thinking the control module (head unit), but it never acted funky. I did test the blower with a motorcycle battery and it worked just fine.

Click to expand...

Put a multi-meter in line while you are testing the blower. If you measure higher than specified resistance you will know why you're not having function of the blower. I don't remember what the running Ohms/Amperage is but I'm sure it's available somewhere online.

As a temporary alternative,hot wire the blower with an inline switch and fuse so at least you have heater function !!

All of these electrical parts go bad after 8-10 years and will drive you nuts trying to track them down. This is not just a GM issue...it's happening across ALL brands.

Follow your instincts and Good Luck !!

Yukon John said:

Put a multi-meter in line while you are testing the blower. If you measure higher than specified resistance you will know why you're not having function of the blower. I don't remember what the running Ohms/Amperage is but I'm sure it's available somewhere online.

As a temporary alternative,hot wire the blower with an inline switch and fuse so at least you have heater function !!

All of these electrical parts go bad after 8-10 years and will drive you nuts trying to track them down. This is not just a GM issue...it's happening across ALL brands.

Follow your instincts and Good Luck !!

Click to expand...

Thanks for the advice...I had a electronics teacher from a vocational high school suggest the same thing. I'll will be blown away if this is the problem.
Shouldn't I be able to read some voltage at the pins when the 2-wire (orange and red) is disconnected from the blower? I could get 11.5v if I grounded the red wire, but nothing if tested orange and red, with the blower on max. Thanks again!

Johnb21 said:

Thanks for the advice...I had a electronics teacher from a vocational high school suggest the same thing. I'll will be blown away if this is the problem.
Shouldn't I be able to read some voltage at the pins when the 2-wire (orange and red) is disconnected from the blower? I could get 11.5v if I grounded the red wire, but nothing if tested orange and red, with the blower on max. Thanks again!

Click to expand...

Remember...you are dealing with a multi voltage set up. A 3 speed blower system will receive 3 different voltages to achieve the 3 different speeds. If you have too much resistance in the winding of the motor, it most likely won't run at the lower voltages. Your test of the motor with the Motor Cycle battery makes sense on the surface but you are hitting it with 12 volts head on and it is running. Now...the test is to read the RESISTANCE in OHMS in line with the motor at 12 volts. If the resistance is beyond specified numbers you may be getting a total drop out of the resisters trying to run that motor at any speed. In my situation, I was ignoring this thinking that my problem was upstream of the motor when all the while the motor was shot...even though it would run on the bench...until it got hot...then it would quit !!!

Get or find on line a section on troubleshooting this in a GM Shop Manual for your truck. There is a procedure for testing this system.