Rear blower not working

[Jobi-Wan Kenobi]

So my Tahoe has the automatic dual climate control. A few weeks ago the rear blower stopped working. I do have power to the two plug for the motor. Is it just that motor is bad? Messing around with this a tonight. If I fiddle with the controls in the back seat I can only get the display to show "off". Is this anything related? I've never actually tried to use them before.

 

[Fless]

Are you using it in Auto or manual mode?

If you can access the motor contacts, connect 12v directly to it and see if it runs.

 

[Jobi-Wan Kenobi]

@Fless it doesn't matter what I have the switch up front set too. It doesn't run at all. I haven't tried connecting 12v directly to it yet though.

 

[Joseph Garcia]

As @Fless suggested, your next step is to put 12 volts directly to the motor and see if it runs. If not, you have your root cause.

 

[Kosherpotatoes]

So not the OP, however. Im running into the same issue. Ive provided 12v power to the fan and it works. Ive replaced the hvac control module, fan speed capacitor, and the over head control and this has Auto on it if that makes a difference. Nothing seems to turn the fan on, same as OP the rear controlls always show off. Looking for further help in diagnosing it. Any help would be great.
Diagnosed thus far:
Rear blower motors good. Confirmed by adding 12 volts to the fan.
Actuators work when I change the temp and the position it should blow for feet and over head
Replaced fan speed capacitor. Has 3 wire input 2 wire output
Replaced hvac control module on the rear where you have red and Grey labeled mounted to the rear system between the 2 actuators.
Replaced only over head unit in the front.

Verified power through all fuses. Im getting 12v power to the capacitor for the fan speed but getting no output power. Ive tried 2 different ones. One new from Amazon another from a pulled unit. Surely i dont have 3 bad of those which is my worry. Sorry for any odd formatting. Im on mobile.

 

[swathdiver]

Time to get out the shop manual and bi-directional scan tool and follow the troubleshooting guide after pulling the internal codes.

 

[Kosherpotatoes]

Time to get out the shop manual and bi-directional scan tool and follow the troubleshooting guide after pulling the internal

No lie, book says with this issue take it to a dealer/ shop with equipment to troubleshoot it. Ill update when i get a solution.

 

[6speedblazer]

Check for power to the blower with a load. I fixed this on my 05 xl Denali and it had me scratching my head a bit at first.

I had 12 volts going into the blower module and modulated voltage out based on fan speed request, however blower was still inop. Tested blower with 12 volts from an M12 battery and it worked perfect. I was testing with my multimeter and not a loaded device like an incandescent test light. My meter would read 12.5 volts but a test light would NOT illuminate. I traced the circuit back and found a burnt power feed for the rear blower behind the drivers kick panel.

i spliced around the OEM plug with a new single wire connector and its been going strong now for a few years.

 

[Jobi-Wan Kenobi]

Haven't had much chance to get back to looking at it but same as others that have commented the blower does work with 12v directly applied.