Electrical Mystery in Chevy Tahoe

I have a 2004 Chevy Tahoe Z71 with an electrical issue that has confounded two repair shops.

This past summer the blower on the ac in front stopped working.

Local guys replaced the resistor which appeared to have blown out, then the fuse blew again within an hour or so, then they replaced the blower, fuse blew again…

For months this has been going on. I took it to Chevy. They couldn’t even get the fuse to blow and said they had no idea, (and I quote) “It’s the bizarrest thing ever…”

So, now I drive around with a box of fuses. Last fuse lasted a month, until yesterday.

I have no idea what triggers it to blow.

I thought maybe it was the summer heat, but yesterday I was proved wrong. PLEASE HELP!

I need this blower to work reliably - it’s essential and my car only has 50,000 on it, I don’t want to have to get a new car.

first find out if any other things are on the same circuit. if there is then that may be the culprit. if not then it may be a wire that is frayed and at times it "grounds " out and blows the fuse.
we had one a while back that the crankshaft sensor wire hit the steering idler arm on turns and grounded out causing the car to die. you just never know what you run into.
good luck

There Are GM Technical Service Bulletins Pertaining To HVAC Blowers On Several Models (14) & Model-Years, Including 2003 - 2006 Tahoes.

This pertains to some vehicles with Automatic Temperature Control HVAC Systems. Blowers on problem vehicles either may not shut off or could be inoperative. The fix is to replace the Blower Control Module.

I’m not saying this is what’s wrong, but rather alerting you of a problem. The bulletin doesn’t mention blowing fuses.

You mention “two repair shops” and taking it to Chevy. Was it a large, high volume dealer ? Have they checked TSBs ?

I sometimes find that problems of this nature are best handled by a large volume Chevrolet or GMC dealer where they are famliar with the specific vehicle / specific problems and see lots of HVAC issues.

I would at least call some high volume dealers and run this past the Service Director and ask if this sounds like a typical blower module failure and something they can easily remedy. I’d strongly consider taking it to the dealer with the most promising response to your query.


Thanks for your response :slight_smile:
The front blower is the only thing on that line. And, lots of times it blows when the car is off - or right when I start the engine. In other words, it’s working when I turn off the car, and when I restart it’s dead.
I do know the trouble began when I got a new charger for my cell phone which works off the cigarette lighter outlet. But… it’s not always the case that the phone is plugged in when it blows.
They have traced the line as far as they “can” and don’t see any issues with the line itself.

The Chevy place I went to is high volume service shop. But, I think it’s a matter of time they are/are not willing to spend on my car. They said they took it out for a drive a couple times to see if they could get it to blow (with the sensors hooked up) and it wouldn’t blow.
I will call to double check with them about the “blower control module”… but they had my vehicle for almost 2 weeks and couldn’t solve it.
Thanks for your suggestions.

If it was mine I would go to a salvage yard get, and try a new blower motor and wires.
My logic is the variable resistor has blown a couple of times, so the problem is after the resistor.
The only things after the resistor are the wires to the blower motor and the blower motor.

There could there be a short in the wiring harness where the protective coating has worn off and the wire is exposed to metal and shorts out.

Have seen a lot of melted connectors for the resistor/ speed controller on these trucks. Try replacing the pigtail it’s available in AC Delco.

“lots of times it blows when the car is off” This is a big clue to the trouble I think.

Since you say the fuse can blow out even when the ignition is OFF then the trouble is with the wiring between the fuse and the next blower power control point in the line which I assume to be the blower relay. The line is shorting to ground somehow. If that is correct the easiest thing to do may be is to cut the original wire at both ends and just run a new wire between those points.

I go with the pigtail replacement. I also think you should monitor the amp pull on the blower. Have you verified that the fuse used is of the correct value? Does the blown fuse have the appearance of something happening slowly or is it clearly an instant blow from a dead short? Perhaps several paramets have aligned so as that the value listed for the fuse is not adaquate for the blower circuit, even when things are working right. We do see the melted pigtail condition, that certainly was not a well thought out design.

Every time I see something like that, it’s due to something else having a poor ground, so that the power finds it easier to go backwards through something else to get to ground. Essentially you would be putting that blower in series with the component with the poor ground, and the blower has relatively low resistance compared with other things in the truck, so it’s easiest to go through it, and then that’s also why it is spinning even when the switch is off. Next time it blows, check everything electrical that you can think of to make sure it works, and if you come down to one thing not working, or perhaps working dimly due to a dirty ground, that would be the place to start, cleaning the ground, or running a jumper right to the battery ground and seeing if that makes it work properly.

The blower speed control has typically operated on the theory of “poor ground”. What I mean is the speed is controled by providing resistance in the ground side of the circuit. This is why when the resistors fail all you have is a “high” speed blower setting (meaning only minimal resistance to ground). I am not looking at a schematic of the 2004 and I am concluding at my own peril that this technique is still in use in the 2004 Tahoe

Thanks for all the suggestions. Unfortunately, not being a car-person myself, I am at the mercy of the repair shop. Tonight I just kept replacing fuse after fuse, they’d blow as soon as I turned the fan on. Couldn’t get a single one to keep working. Thankfully it was a clear nt, and I didn’t need the defrost. I will take all the suggestions in to the shop tomorrow. And, keep my fingers crossed.

Please post back with your findings. I was suggesting a salvage yard blower to minimize cost, 20 bucks vs 60 for the part(guess) for a diy try, just in case there was another issue.

The one ground you can do yourself is under the hood, right up above the steering column and maybe a little more toward the center of the vehicle. It’s right up at the very top rearmost part of the engine compartment. Disconnect the end that goes to the body and scrape or wire brush the end and the thing it connects to. You just need a wrench and ten minutes of free time. You have nothing to lose. Reconnect it and don’t even run the engine until you do. If it’s the same as on my pickup, you will be looking at it in seconds.

The blower fan may be jammed and and not free to move. If it is that would most likely cause the fuse to blow out. Try disconnecting the connection to the blower motor and see if the fuse blows out then. If it doesn’t then something is most likely wrong with the motor. You could also try running power directly to the motor and see if that works. The relay could be pulled also to see if the short is before or after it.

I am wondering about the issue with the fuse blowing out while the ignition is off. Apparently that isn’t a problem at the moment since you say you have to turn on the blower to make the fuse blow out.

Do you know of the “pigtail” that I and one other person has mentioned? what I mean is this is something you must check out.