HVAC fan hit or miss and maybe remote start issue?

Keithinsc · March 29, 2023

2017 GMC SLT with 6.2 and auto/dual zone HVAC. Stock as it came from the showroom aside from the cap and some window tint. 65,000 miles

HVAC fan will work fine for a few weeks, then it will decide to not come on when you start the engine. Mode changes still work, you can hear them cycling. Fan might come on the next time you start it, might not. May take 4 engine start/stops before it comes on again. Then it may work fine for a month. Been acting like this for about a year.

I've pulled the blower and it spins free, all connections seem tight. I've smacked it with a screwdriver handle to see if that would 'wake' it up. Checked all the fuses and wiggled a ton of wires. No luck. Doesn't seem mechanical or electrical, but more computer control glitch. Something needs a software update??

Possibly related, when I use the remote start, the fan will not come on like it used to after a minute. Makes pre-cooling or pre-heating pointless. But once I unlock and put the key in the ignition the fan will then work (unless it is having one of its' moods). BCM fault? I don't have a GM tec scanner, my cheapo doesn't show any codes. Any suggestions for a scanner to read body errors?

Anyone have a problem like this?

MikeBMW · March 30, 2023

I had a friend at work who had a similar issue and an issue with the blend doors on the AC system, as well.
I brought in my Autel MaxiSys scanner to relearn the AC system and it solved the issues.
A repair shop wanted $800 dollars to replace all of the blend doors until I did the fix for free.
Go to a reliable shop and have a scan on your truck. Might be a simple fix, as I mentioned.

silveradosid · March 30, 2023

your blower has a dead spot on the armature and when it stops there it wont start. there is many contact points on the armature so it will work a long as it does not stop in the one spot. replace the blower motor

Keithinsc · March 30, 2023

That might be an idea. Easy enough to check, I can leave the glovebox and cabin filter out. Next time it doesn't work I can reach in and give the squirrel fan a spin to 'kickstart it'.

But it still leaves the issue that the fan never works on remote start. I can remote start it after leaving the HVAC set on high medium or low AC or high medium or low heat. No fan. Unlock the door and insert the key, turn to run and the fan immediately starts. Unless it is having a mood!

9 hours ago, silveradosid said:

your blower has a dead spot on the armature and when it stops there it wont start. there is many contact points on the armature so it will work a long as it does not stop in the one spot. replace the blower motor

Keithinsc · April 2, 2023

The dead spot on the blower is not the issue.

Fan was DOA after I got gas after dinner with my parents. Worked fine for the hour drive there, and then about 40 min home. Stopped for gas and it was inop for the remaining 20 min drive to home.

I left the truck running (so it would not reset) and got out some tools. Pulled the glovebox and air filter. Reached in and gave the fan a spin. No luck.

Turned the truck off and on a few times over a period of 20 minutes. Came on after the 3rd try, while I had it apart, I pulled the power connection from the fan to check the voltage. As expected, motor died when I pulled the plug. Tiny pin connections so I could not get my meter probes in there. Plugged it back in and no fan again.

Checked the frt fan fuse at the fuse block right next to the glovebox. 40amp at position 43 (?). Checked good and had 10 v at the fuse.

Any ideas?

Keithinsc · June 11, 2023

OP here. Just in case anyone's search brings them to this thread.

Finally bit the bullet in May and took the truck to the dealer.

Voltage control in the Heater control (dash dials) was failing and burnt out the blower motor. Motor was showing higher than normal resistance and that was causing poor speed control feedback.

$900 later, and the truck HVAC is working as it is supposed to.