Thread: 04 Envoy blower motor and blower module problems

Hello. I hope someone can help with regard to our 04 Envoy. We replaced the blower module in July due to the fan not shutting off - even with car off. Took care of problem for a while. Then fan stopped working off and on over the past month or two. Last week stopped working all together. We replaced the blower module again (for an automatic HVAC) with no change. So we then replaced the blower motor itself. That worked, however, the fan is back on high and wont shut off or go into a lower setting even though the key is not in the ignition. What could be the problem?

Any time the fan is on with the key off, it's a bad speed control module. Your history hints at flaky, overheated, and oxidized connectors on the wiring harness that connects to the module, but that's less of an issue until you solve the continuous operation. Almost never reported to be the HVAC control head

What did your connector look like last time you inspected it? Any melting?

Say - when you say blower module, you DO mean the one down by the blower motor behind the glove box? Not the control head mounted in the dash below the radio?

Do you have a voltmeter and want to go poking about in the circuits with my guidance?

Yes, I mean the one behind the glove box on passenger side (its called a blower resistor). History: when it went out in July, we went to our dealer to buy the replacement resistor. They said that part had been replaced with a different one. Problem was that the old one had seven prongs, the replacement had five. We had to do some splicing and get it connected. It worked, but our car surged and would die at idle if the air cond was used. We took it to a mechanic and he fixed the wiring and the car wouldn't die anymore. However, the fan stopped going on sometimes. It would have to be in low or off when car started to get it to work. Last week it wouldn't work at all. So, we went online to buy another blower resistor on Saturday - found that Advanced Auto had the replacement for our Envoy that had seven prongs like the one that came with the vehicle. So we had to buy a pig tail to get it back to original manner. Problem was there were 7 colored wires, 3 small black. One of the colors (green) didn't match the instructions online (which said there would be a blue wire). We used the green where the blue would go. We are guessing its a wiring issue - the car is fully loaded with every option you would want, which is a curse if you have electrical issues. We do not own anything to check currents. Is this easy and is this something that could be purchased at a retail store since it's Sunday night? Such as Walmart? Thank you for any assistance!
PS forgot to say that everything looked fine with the resistor that we took out that had been replaced in July. It didn't have condensation or any melting or signs of issues.

It sounds like the dealer screwed you with some bad information. Sorry for the issues, I hope you can work it out.

If you have the manual controls there should have been 7 pins on the blower resistor. Sounds like the dealer screwed you on the resistor.

Originally Posted by ckkk1

Yes, I mean the one behind the glove box on passenger side (its called a blower resistor).

Got it. NOW - do you really have the solid state blower speed control module that costs $80-100 that goes with the automatic/digital HVAC control system with rotary knob temp control like this

6.jpg

or you have the cheaper $30-40 resistor pack that goes with the manual HVAC controls that have up/down temperature sliders?

5.jpg

You say you have the automatic system, but the proper speed control module for that does not have 7 wires. Only the manual system has seven wires.

History: when it went out in July, we went to our dealer to buy the replacement resistor. They said that part had been replaced with a different one. Problem was that the old one had seven prongs, the replacement had five.

The dealer is a goofball, or something else is weird here. See my question above.

We had to do some splicing and get it connected.

Where did the instructions come from?

It worked, but our car surged and would die at idle if the air cond was used.

That's a simple issue, and (as odd as it may sound) involves a $5 cleaning of your throttle body. Nothing directly connected to the HVAC system except the idle can't stay constant when the AC compressor cycles on and off. It's a sticky throttle body problem.

We took it to a mechanic and he fixed the wiring and the car wouldn't die anymore.

What exactly did he fix? Did it also involve a throttle body cleaning?

However, the fan stopped going on sometimes. It would have to be in low or off when car started to get it to work.

Depends on the exact nature of the miswiring.

Last week it wouldn't work at all. So, we went online to buy another blower resistor on Saturday - found that Advanced Auto had the replacement for our Envoy that had seven prongs like the one that came with the vehicle.

That would be because you have the manual, not the automatic, HVAC system.

So we had to buy a pig tail to get it back to original manner. Problem was there were 7 colored wires, 3 small black. One of the colors (green) didn't match the instructions online (which said there would be a blue wire).

Can you post a link to these on-line instructions? Might clear up a lot. I know about a 7-wire connector, but not another one nearby with 3 black.

We used the green where the blue would go. We are guessing its a wiring issue

As an electrical engineer with a 38 year career, I can assure you that guessing is bad.

- the car is fully loaded with every option you would want, which is a curse if you have electrical issues.

Do you have the rotary temp controls or the up/down sliders?

We do not own anything to check currents. Is this easy and is this something that could be purchased at a retail store since it's Sunday night? Such as Walmart?

Walmart, and any auto parts stores, have them. Harbor Freight has some real cheapies that are good for a first timer. But let's figure out what kind of system you have first.

Thank you for any assistance!
PS forgot to say that everything looked fine with the resistor that we took out that had been replaced in July. It didn't have condensation or any melting or signs of issues.

Here are pictures of the three various possible modules.

Manual module. 7 wires input, 2 wires output to the blower
1.jpg

Same one, different view
2.jpg

Automatic module. 3 wire control input, 2 wires output to the blower. Old and new style
1.jpg

Automatic module (newest style). 5 wire connector harness. 3 still used for inputs, 2 for outputs
4.jpg

I had the same issue with my 2005 trailblazer with the auto HVAC. I ended up having to replace the control unit, resistor pack, resistor wiring and blower motor. I started with the wiring and resistor pack (didn't stop the problem), finally fixed it by replacing the control unit and blower motor.

Originally Posted by Vicompc

I had the same issue with my 2005 trailblazer with the auto HVAC. I ended up having to replace the control unit, resistor pack, resistor wiring and blower motor. I started with the wiring and resistor pack (didn't stop the problem), finally fixed it by replacing the control unit and blower motor.

I would rather not start using the phrase "resistor pack" for the speed control module because it could confuse somebody going to the parts stores. The manual system has a resistor pack because it actually has power-dissipating resistors in it (and a relay for speed 5) that have to hang out in the airflow of the blower to get cooled off. But the automatic system has a solid state design that uses a power FET (field effect transistor) inside with a finned aluminum heat sink to go into the airflow. No visible resistors. Thanks.

Sparky's Answers: 2003 GMC Yukon Bower Erratic / Not Working

please read the highlighted red text if you scroll down on this thread. I'm guessing this is what is going on here. I have the same problem with my tahoe. I verified the signal going into the blower control module from the climate control module with an oscilloscope and verified no voltage going to the blower. I have a new climate control unit(shouldn't have replaced this, waste of money) and have gone through two of the updated blower speed control modules and both have had this intermittent problem. My next step is to replace the FET in my old unit. I'll be damned if I'm going to replace a perfectly good blower motor for a GM design flaw when they "updated" the module. I've been chasing my tail on this one for weeks!

Originally Posted by bruhaba

Sparky's Answers: 2003 GMC Yukon Bower Erratic / Not Working

please read the highlighted red text if you scroll down on this thread. I'm guessing this is what is going on here. I have the same problem with my tahoe. I verified the signal going into the blower control module from the climate control module with an oscilloscope and verified no voltage going to the blower. I have a new climate control unit(shouldn't have replaced this, waste of money) and have gone through two of the updated blower speed control modules and both have had this intermittent problem. My next step is to replace the FET in my old unit. I'll be damned if I'm going to replace a perfectly good blower motor for a GM design flaw when they "updated" the module. I've been chasing my tail on this one for weeks!

Ok, well, first post I see so welcome... And... If you look at the date this was an old post from December of 2011... Totally different ball o worms...

Originally Posted by McGMT

Ok, well, first post I see so welcome... And... If you look at the date this was an old post from December of 2011... Totally different ball o worms...

yeah, I noticed that, thanks...I still came across this thread in my research on this problem. Link still applies IMO. Not a different ball of worms? Many people experiencing this out there, so it's good information to spread.