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Auto Air Blower Fan Intermittent

28K views 19 replies 13 participants last post by  rhenryiii 
#1 ·
2003 Envoy XL with the automatic (electronic) HVAC controls.

About a week ago the (front) blower fan quit working. I pulled the connector out and checked the voltage at that plug. 11.77V on all levels of fan setting. So I figured the blower motor must have been bad. I even hooked 12V from the battery directly to the blower motor...nothing.

Anyway, $150 later (I was on a time crunch so couldn't do much shopping around) from the Chevy dealer I had a new fan. I even plugged it in at the dealer and the fan started spinning and responded to the fan settings. So I installed it and it worked for a day...now it seems to be intermittent (I'm not there to verify but that's what it sounds like.)

So, does this sound like a control module problem? (I'm thinking now the 11.77V on all settings may not have been what I should have been seeing. Does the controls vary the voltage or pulse the voltage to control fan speed?)

I did check all fuses and they are fine. There is a chance the old blower motor was fine...my hooking it to the battery wasn't the most scientific way. Like I said, I was on a time crunch at the time...

Any help would be very very appreciated...Thanks!

Andy
 
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#3 ·
welcome...
this sounds familiar.
Did you come over here from chevytalk.com?
hopefully guys on here can answer your question about your digital AC.
 
#4 ·
Yep, I came over from ChevyTalk. Is that considered double-dipping on posting? Which reminds me I need to reply back on that site too.

Anyway, over at ChevyTalk there was mention of looking at the factory ground and improving the connection. The ground and power wire for the blower motor go straight into the motor control board. I didn't look real close, but I didn't see any external ground...

Any other thoughts out there? I really thought this would have happened to others. But then again, I like to be a leader in something. :eek:

Andy
 
#5 ·
no. no double dipping...
just that I read the post- and was like.. hmmm someone else has that same problem... but I had recommended you head over here to ask these guys.
 
#6 · (Edited)
It almost sounds like a blower resistor, I had a blower on an older sunfire with a similar problem only that I basically had low and high fan speeds nothing inbetween, these are usually located near the blower and look like a memory wafer

it's #4 in this picture.



*AS NOTED BELOW THIS IS CALLED THE CONTROL MODULE, STILL LOOKS LIKE THE PICTURE THOUGH

May not be solution but a good try anyways
 
#7 ·
:iagree: kellyc, but in the original post he said it was the auto HVAC. The analog HVAC uses the resistor, the digital uses a speed control module that auto changes motor speed. It's mounted in the same place as the resistor, under the dash - behind the glove box.
 
#8 ·
Sorry about that, now that I look at the description yes they do call it a control module, my bad.

Similar function though that I would think would yield the same result.
 
#10 ·
I clicked on this site specifically to see if anyone else is having this problem.
I also have a 2003 Envoy XL SLT and mine also just started having the same problem. When I turn the blower fan speed all the way up, sometimes it will blow hard, sometimes it will barely blow at all.
I'll be watching to see if anyone has a confident solution.
Thank You in advance.
 
#12 ·
They're all dying! My Automatic Climate Control is working intermittently as well. I turned it on last week, and no matter what the fan wouldn't come on at all. Left it off for about 10 mins while driving, and it worked fine. Sometimes the fan speed will change when I don't tell it to. Is this still sounding like a motor control issue?
 
#13 ·
They're all dying! My Automatic Climate Control is working intermittently as well. I turned it on last week, and no matter what the fan wouldn't come on at all. Left it off for about 10 mins while driving, and it worked fine. Sometimes the fan speed will change when I don't tell it to. Is this still sounding like a motor control issue?
You know, your problem is a little tougher to diagnose.
Not coming on at all, sounds like the speed control module.
Changing speeds sounds like the control unit mounted in the dash.

I don't have the auto unit (though, I have experience with other cars that have had that style unit),
don't they sometimes change fan speeds automatically? Isn't that how they work?
 
#14 ·
They do change speed automatically, but only if you have it set on automatic. I usually set mine on a specific fan speed and direction, because if I don't for some reason it defaults to blowing air at my feet. I'm gonna give the speed control module thing a try and see if that works.
 
#15 ·
Intermittent blower motor

Hello all, I am new to the site and i am looking for some info. I have a 06 trailbalzer and the fan motor quit. I checked voltage at the fan connector and i have 11.87 at the high setting and 9.03 at the low setting. It has electronic temp control. I hooked the blower motor to an external 12 volt power source and the motor seemd jerky as it came up to full speed. I am suspecting the motor is bad. anyone else found this?
 
#16 ·
Blower intermittent

I replaced the blower motor resistor and harness on my 06 Envoy SLE last summer. Everything worked great until recently. Now the motor cuts out. No power at any speed. I checked the resistor, harness, connections and fuses, all fine. However, if I move / shake the wire bundle to the harness, motor comes on. I check every connection and cannot get it to cut out until it does it later on its own. Any suggestions? :bonk:
 
#17 ·
This may not be the solution to everyone's problem of intermittent fan operation, but I had the same problem for the past year or so. Fan would work fine for months, and then all of a sudden, quit, then suddenly come back on, sometimes days or minutes later.

I thought control board was bad, and pulled the blower motor out. Tested the voltage across the plug w/ a voltmeter, and all was fine. Just for the heck of it, plugged the blower back onto the plug, and it worked fine.

Long story short, it ended-up being a bad blower plug/motor connection. When I wiggled the plug back & forth a little, the blower would start & stop.

I bent the prongs on the motor down a little, plugged it back in, and has been working fine ever since.
 
#18 ·
Blower Motor

I know this is an old post but I would like to put this up there in case it helps someone else.

Had issue with blower working then not working. I had already replaced the resistor a few years back so I was really confused. I picked up a new resistor and replacement blower just to be safe.

Well roadie had mentioned to check out the wiring harness that goes to the resistor for a melted ground wire. Well.... Bingo that was the problem. Replaced with a part form auto zone for just over 30 bucks, spliced it in and everything working like it should.

Thank goodness for this site. It has saved me hundreds of dollars at the shop or dealership.

Thank You Roadie, other users for the help, and big shout out to trailvoy!!!!
 
#19 · (Edited)
I'd like to add that I've seen many intermittent faults where each device and wire run in a circuit would check out OK if tested individually, but would occasionally work or fail only with the vehicle in motion or as wiring harnesses were flexed. This would (seemingly) naturally cause one to assume an intermittent open circuit in the wiring harness. Often, though, a new wiring harness would work at first, but failures would come back very soon.

The problem often lies not in the wiring, or the devices, but in the connections between them. Clean, bright contacts with positive contact are the way to go. As vibrations from the drivetrain or road noise course through everything in a vehicle, the mating surfaces in pin & socket or spade connectors will rub against each other ever so slightly, causing wear. Also, in the case of blade/spade connectors, the spring tension in the female connector can relax over time. The "book" fix is to repair by replacing the connectors, if available and practical, or by replacing the harness and connected components together. As you can see, that can get expensive in a heartbeat. Not to worry, though.

I grew up riding with my dad on service calls, watching him repair all makes of home appliances. One trick I picked up from him was to, very slightly, tweak the pins or blades in a suspect connection to renew the tension in the mated connection. This often restores a solid electrical connection by moving the point of contact to a previously unused portion of the mating connectors as well as putting some much-needed tension to help maintain a solid contact as the connections in the machine/vehicle are subjected to vibration during operation.

On connectors with multiple blades, I like to give each blade a very slight twist. On ones with multiple pin & socket connections, I'd give each pin a tiny lean. Not so much that the connector is hard to install, mind you.

This has solved more than a few intermittent electrical faults for me. Most recently I've cured the intermittent ABS warning light on my '02 TB, where a wheel speed sensor was sometimes just an open circuit.

As a very young Soldier I showed my shop foreman this trick, and he tried calling BS. He didn't think a damned turret mechanic could fix anything, but he had to give me props after I fixed a tank he'd had a crew of hull mechanics on for a week, swapping parts and pointing fingers, playing the blame game. Good times :)
 
#20 ·
Intermittent Fan in Heat or Cool mode

I have a 2003 TB ELT LS with the auto controls. Sometimes in the winter, the fan will quit. After you turn off vehicle and it sits for a while, it will work and may go weeks before it fails again. I found that if I turn off vehicle and do not turn the fan to lowest setting, it may not work the next time I start it.

In cool mode, it is similar in summer but happens more often. Not sure if this is a contributing factor but it seems to happen more often when A/C is set on auto temp, with temp controls at max cool temp and fan goes to high speed.

Blower control module or could it be something else?

Thanks
 
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