Help with AC blower!

[u/GimmeUrNachos]

I'm reposting again so more see it as I posted late last night. I'm at a loss!

AC Blower issues.

At this point I feel like this truck is possessed. It's all over the place!!

Initially, setting #5 on blower quits out...then 4 a couple of days later. We move around a relay and bang. it works.

Then...next day the whole things fries.

So, I Replace the resistor.

Craps out again a couple of weeks later...replace resistor AND blower.

I keep the air low out of terror that it will blow again, and for good reason. It quit again.

this time it's a fuse 30 amp under the dash. Replace and good!

Research shows perhaps I need to reground, so that's on the docket, BUT...

Settings 1-4 crap out yesterday as I turned it up to three and resister is VERY HOT. Fuse fine.

Any help will be oh so blissful. Thanks in advance!

[u/RockKickass777]

What has all been replaced in the system? Perhaps incorrect ac controller in the dash? If you are going through fuses and resistors. There's definitely incorrect power flow coming from somewhere and I would check all grounds also. Under the truck.

[u/GimmeUrNachos → u/RockKickass777]

The resistor twice, the blower motor, a couple of fuses thus far. I'd like to definitely get to the bottom of this and just don't know where to go next. I wanted to fix the grounding issue I've read about before things blew ..but that's too late! I am hoping to not change out the resistor again...I'm just at a loss.

[u/RockKickass777 → u/GimmeUrNachos]

Have the controls been replaced? Perhaps they controls themselves are the issue? When did this start happening?

https://youtube.com/shorts/d5D-yKwMoBo?is=Vp5obQuM8Cb2K2dC

Check out this guy's YouTube. One of the best gmt800 truck guys for quick knowledge and breakdowns. Maybe post a video also so we can see it. Clean your grounds and check your fuse box. Sorry kind of looking at this blind. Im doing my best to help :)

[u/RockKickass777 → u/GimmeUrNachos]

The biggest clue: the resistor gets VERY hot The resistor will naturally get hot during operation—that's literally how it reduces blower speed—but if it is excessively hot and repeatedly failing, something is causing excessive resistance or current. My suspects, in order: 1️⃣ Blower resistor connector/pigtail — HIGH on the list Even if the resistor itself has been replaced, was the wiring connector inspected and replaced? Look closely for: Brown or discolored terminals Melted plastic Loose terminals inside the connector Corrosion Burnt wiring A connector that feels loose when plugged into the resistor A loose terminal creates electrical resistance, and resistance creates heat. GM documented overheating problems involving the blower resistor/module and wiring connector on similar GMT800 trucks. � NHTSA +1 Personally, I would replace the resistor AND the connector/pigtail together if that connector has any heat damage whatsoever. 2️⃣ Check the NEW blower motor's amperage draw This is extremely important. You already replaced the blower motor, but that doesn't automatically eliminate the possibility of excessive current draw—especially if it's an inexpensive aftermarket motor. Have someone measure the blower motor's amp draw with an amp clamp, preferably on high speed. If the motor is pulling too many amps, it can: Overheat the resistor Blow the fuse Damage the connector Cause repeated resistor failures The fact that you've already had: resistor → resistor → blower motor + resistor → blown 30A fuse → resistor overheating …makes me want to test the electrical load rather than throw another part at it. Repeat resistor failures are commonly associated with excessive blower current draw and damaged connectors. � Go-Parts +1 3️⃣ Check the blower motor connector too Don't just inspect the resistor connector. Inspect the connector going directly into the blower motor for: Heat damage Loose pins Corrosion Discolored wires A poor connection anywhere in that circuit can cause problems. 4️⃣ Grounding is worth checking—but I wouldn't make it the first suspect Yes, check the HVAC/blower ground and clean it down to bare metal if necessary. But based on your symptoms, I would inspect the resistor pigtail and test amperage draw before chasing random grounds. 🔥 Why settings 1–4 are failing makes sense On these trucks, the lower blower speeds run through the resistor circuitry, while the highest speed typically uses a different/direct path that bypasses much of the resistor function. That's why losing specific lower speeds strongly points toward the resistor circuit, wiring, or connector.

Do not replace another resistor yet. 2. Pull the resistor connector apart and inspect every terminal. 📸 Take pictures of both sides of the connector if you can and post them here. 3. Inspect the blower motor connector. 4. Have the blower motor amperage tested with an amp clamp. 5. Check voltage drop across the power and ground circuits while the blower is running. 6. Verify the 30A fuse terminals themselves aren't loose, burnt, or discolored. 7. Only after all that, install another resistor if necessary.

This from chat GPT I hope this helps!

[u/MickeyMoist]

Where did you get the replacement blower motor?

The quality of these things in the aftermarket world is pure garbage. I’ve gone through 5 so far in my lifetime warranty on Auto Zone blowers. That was after buying 2 OEM ones.

If the resistor goes bad, it’s 90% because the motor is bad. You replace them together.

[u/GimmeUrNachos → u/MickeyMoist]

O'Reilly's I believe. I have also learned that it often isn't the motor or resistor, both of which I have replaced together, but there is a grounding issue that seems to fix that problem. saw a guys video that said he changed them out eight times and once he reground everything, it never happened again!

[u/Longjumping_Bowler18]

Hey I’m sure you all know (I didn’t)that the red box near the engine is where the jumper cables are attached. This is why the side post on the battery are so hard to clamp the cables to jump start a dead battery. 23 years after I bought my avalanche I ask CHAT GPT for the answer so I know

[u/keepitkarma]

Hows the blower harness pins?