Blower motor control processor [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: Blower motor control processor


Davin
07-27-2008, 04:23 PM
Does anybody know where I can get one besides the dealer.? And how much is it. My blower motor is running constantly and that appears to be the problem

the roadie
07-27-2008, 04:39 PM
Do you have the digital controls or the analog one? The circuit and controls are different.

If you have the digital (as I do), it may be a simpler and cheaper failure, since the final power stage is a power FET mounted near the motor that converts a pulse stream (PWM) from the body computer (expensive unit under the driver's side rear seat next to the rear fuse block). The digital level PWM gets amplified by the power FET (transistor switch) and sent to the motor to vary its speed continuously (instead of the distinct steps of the analog control), but if the FET shorts out, all you would get is full-speed no matter what the control attempted to command.

If my parts list is right, that's a GM # 52494707, $86 at parts4chevys.com ($137 list price) and not likely to be an aftermarket item. But that's for my 2004 model. Yours may be different and I can't tell because you didn't fill out your profile yet. But welcome to trailvoy.com, where we try to answer everybody's first question (and all the later ones...) because we're nice folks. :D

If it's the dash unit, that's $150-$250, and again - a dealer-only (or ebay or junkyard) part.

Davin
07-27-2008, 06:12 PM
It is digital and is running all the time. The only way to get the blower to turn off is to pull the 40 amp fuse under the hood or disconnect the battery.

RayVoy
07-27-2008, 07:12 PM
In case you need translation on Roadie's post :laugh:, he gave you the part # for the unit u require. It's called a Blower motor control module. You can find it under the dash, behind the glove box, mounted very close to the blower motor.
Very easy to change. There is a number of threads on the topic, try a search using the above name, or, the name of the non-digital unit (blower motor resistor assembly).

Davin
07-27-2008, 07:18 PM
Thanks for the help. I already have the module out. Im just trying to figure out if its a dealer only part. And if it is available aftermarket where I could get one

Davin
07-27-2008, 07:22 PM
The part number on the moddule that I have is 52409643

the roadie
07-27-2008, 08:37 PM
In case you need translation on Roadie's post :laugh:, ...Yeah, yeah. :p I started my career in power semiconductors so if mine failed (I was poking around in it a few months ago but it was a simple connector failure), I'd just build another one from parts I have lying around.

I did another search, and drilled down in the rockauto.com site, and found they carry the AC Delco replacement part (not exactly aftermarket, but at least it's not from the dealer you seem to shun): (but again, I don't know your year vehicle, so I might have found the wrong one)

ACDELCO Part # 1580567 More Info {replaces 93803636 #89018778, 93803636}
MODULE,HTR & BLO & A/C CONT w/A/C FRT AUTO/AUX CONT(CJ2) $61.79

At napaonline I found nothing. Can you take it from here?

85vette
07-27-2008, 08:44 PM
You can look on Ebay. I bought a used one for one of my trucks for less than $50.00. My 98 C2500 did the same thing your's is doing. I had to pull the fuse to make it stop. The control went bad.

vrekow02
07-30-2008, 12:22 AM
My 2002 trailblazer A/C blower motor is stuck on high, even with the ignition off. Anyone ever have this problem, and what was the fix.

85vette
07-30-2008, 08:48 AM
Not sure, but you may have a bad ignition switch. Did the blower start sticking on high first, or did both problems occur at the same time?

the roadie
07-30-2008, 01:25 PM
I can't see a bad ignition switch doing anything but two different things:

1) Applying power to circuits that should only be energized with the ignition on, when the key is off (either RUN circuits or START circuits).

2) Failing to apply power to circuits when it should be, again, either RUN or START circuits.

The fan blower being on high is something that shouldn't happen in either RUN or START circuits, so my bet is on the blower controller module, but that's an item only present in the electronic climate control, not the manual one. vrekow02: can you confirm you have the electronic control? If so, you have the same problem as Davin and need to buy the same module.

85vette
07-30-2008, 01:55 PM
That's why we like you engineers on here.....to make people like me look dumb. That's OK, I don't need any help.....but really, mine is the manual control and it only worked on high, but it did turn off when the key was off. His is running even with the key off, were is it getting it's power source from?

the roadie
07-30-2008, 02:48 PM
That's why we like you engineers on here.....to make people like me look dumb. That's OK, I don't need any help.....but really, mine is the manual control and it only worked on high, but it did turn off when the key was off. His is running even with the key off, were is it getting it's power source from?No, no. I hate even the thought of making anybody look dumb. Owning the shop manual and all the circuit diagrams and figuring out how to read them is an asset, but not a sign of any extra intelligence. It's just a tool.

I'd have to look at my manual when I get home, but the fan draws a LOT of current on high speed. I would have designed it to the power pin bringing 12V to the control module was ALWAYS hot, and didn't go through the ignition switch at all. There's a lot of stuff that is always hot. And if the control module went bad and shorted out inside, then the constant 12V could get applied to the fan motor no matter what the AC control master box advised it to do through the PWM control pin. Like an outside water faucet that was turned on, then the handle broke off - it would never stop flowing.

tblazed
07-30-2008, 02:53 PM
Since it is a 2002 LS it will have the manual AC with 1-5 fan speeds. If it's stuck on High with the key off maybe the relay that supplies power on high speed 5 (relay is part of the resistor assembly) is stuck, the contacts welded together, somesuch. That's what I would look at first.

RayVoy
07-30-2008, 05:33 PM
Right you are tblazed.
Fuse #35 (under the hood), as roadie said is hot all of the time.
Fuse #35 is used by the auto system to power the blower on all speeds, and by the manual system to power the blower in position #5 only.
Position #5, manual system, uses a relay to provide power to the blower. This relay is in the blower resistor assembly and is operated when the switch is in position #5 only. The power to operate the relay is a switched 12v (fuse #44) in the rear fuse box.
The repair, is a resistor assembly replacement.

Atlwrk
02-17-2010, 01:54 PM
Since this thread is so old but relevant I figured no one would mind my hijacking it.
Gonna get a little technical--


...a power FET mounted near the motor that converts a pulse stream (PWM) from the body computer (expensive unit under the driver's side rear seat next to the rear fuse block). The digital level PWM gets amplified by the power FET (transistor switch) and sent to the motor to vary its speed continuously (instead of the distinct steps of the analog control...

I have the manual controls that have been replaced once already (including the harness) for melting the connector. It's been a few months and once again I'm beginning to smell (literally) impending failure. Instead of waiting for it to die I've decided to build my own replacement using PWM control and a FET similar to the digital climate control. Iíll be using the discreet settings from the manual control to establish a voltage reference for generating the appropriate duty cycle. This will all be built into a digital control box (anyone have a dead one they're willing to part with for the cost of shipping??)

A few questions:
I know the controller receives a ~300Hz pwm signal that is amplified in the controller then sent to the motor. Does anyone know if the output pwm sent to the motor is also ~300Hz? The reason I ask is that there is a chip on the digital controls (marked AA539B) that I havenít been able to track down any information on. Is it a monitor, FET driver chip, or a specialized controller that may change the frequency? Iím trying to decide on a good frequency to run and found 1000+ different opinions. I figure my best bet is running what the OEM system runs. 300 Hz would be pretty efficient but an audible hum is unacceptable.

Anyone know or willing to check the OUTPUT frequency with an oscilloscope or DVM (with freq measurement)?

the roadie
02-17-2010, 02:15 PM
I loaned out my home scope to my FORMER son-in-law out of state who hocked it I think. :hopeless And I'm between jobs now so I can't even borrow one from work. :sadcry: Sorry.