Hey everyone, so I recently replaced my HVAC control module because I was having issues with not only the blend doors acting up where I was getting heat on the driver side and cold air on the passenger side, but I also had some lights burnt out and my buttons were worn. I replaced the HVAC control module and then performed the reset procedure by pulling the fuse and then letting it idle, but I’m having an issue where when the HVAC is set to auto the blower motor is blowing at full speed. I’m not sure it’s the resistor because I can still increase and decrease the blower motor speed. It’s just whenever it’s on auto. It wants to blow full speed. It wasn’t doing this on auto with the OEM control module. Should I try the reset procedure again or do I have to go borrow a scan tool? Any help would be greatly appreciated. Thank you.

 

Mine always goes to full speed in auto, I have to reduce it manually, mines a 2003
might be how its supposed to be

 

All the GM vehicles I've owned or still own to date always blow at full speed in auto mode. As soon as you press the auto button, or as soon as you turn on your A/C, it goes to auto mode, where the A/C unit blows at full speed. I've owned an 04 Chevy Avalanche North Face Edition, 02 Escalade EXT., currently own a 03 Escalade EXT., owned a 05 H2 SUT, and currently own a 09 H2 SUT. As long as your A/C works, that's all that matters. My 03 Escalade only wants to blow cold whenever it feels like it. Not sure if it's the blend doors acting up or the actual control module.

 

so I played with it some more trying multiple different reset procedures and now it’s not running full speed anymore and the blend doors seem to be actuating properly but I’ll have to drive some more to see for sure. But now the fan speed is going up and down repeatedly like every 30 seconds

 

okay maybe it’s just a GMT800 thing cause I’ve had a 12 Escalade, 10 Suburban and 09 Tahoe and none of them blew full speed like this on auto. Does your blower motor also go up and down randomly? cause after I let it run for about 10 mins parked on the drive way the blower motor slowed down when the truck reached temperature but then kept surging every 30seconds ramping up and down in speed.

 

There are multiple sensors that will drive the fan to high when in auto, the sun load sensor, duct sensors based on the temp settings,
Try changing the temp setting higher and see if the fan will slow.
The reset method of pulling the fuse is hit or miss in my experience, resetting with a scan tool should work best.
Looking at all the AC sensors with a scan tool is the best option for troubleshooting these type of issues.
Oscillating fan speed is not a GM programed feature.

Neal

 

Tossing this out there also- just because of reference to blower motor / resistor.....
IF the seal (more like WILL) leaks where the black intake cover is (under the front cowling on right side).... Water WILL make its way to the blower motor & the resistor ruining them / creating bizarre issues.... Just tossing it out there for future readers working on blower motor/ resistor faults... The seal on mine was totally dried out & compromised. Easy to check, just remove the cowl (about 10 minutes). I only found this out during a time I had the cowl off to prepare for a windshield change. I would definitely check it, the gasket on the black cover is one of the WILL FAIL items.

 

Thanks for the feedback. I'll keep this in mind.

 

Mine always blows on Max when it's in auto mode and you have to manually lower the fan speed