Write-Up: Blower Motor Control Module Replacement

The only Head schematics I have are what I've posted for you, and one's for the Sunload sensors and passenger heater control. You should be able to diagnose your problem with what I've given you so far.

Great write-up.  Helped me figure out where this was and diagnose it as the problem.  Took me about a half an hour to get changed out and now I have blowing heat again.  Man was it cold last night and this morning with no heat blowing in the car.

J. Chris Davis wrote:

Great write-up.  Helped me figure out where this was and diagnose it as the problem.  Took me about a half an hour to get changed out and now I have blowing heat again.  Man was it cold last night and this morning with no heat blowing in the car.

I went thru a winter in Chicago with no heat due to a blower module out in the riv. It really sucked. I had to scrape inside the car. That's what got me to rivperformance

...wow...in Chicago with no heat Ruben?......man.....

Yep. I would get to work after an hour drive with hypothermia. I figured it out finally and got a new module at the dealer to install. Its a pain working under the dash to replace it. Thanks to this forum I figured out the problem

My turn...
First start yesterday morning and I had no air; warm or cold. No signs of life from the fan motor.

Thanks, Scott, for the write up.

If you can wait for it, try finding a used OEM part - mine was $30. These modules either go bad or last forever, it seems. If you buy from RockAuto: $130, GMparts Direct: $150, dealer: $290.

It's really easy to swap. Best of luck.

If I'm not getting any air or sounds at all, it's most likely the blower motor, right? And not the control module?

Difficult to say. Both can result in motor not working. I'd replace the module first, unless you can remove the motor and test it.

charlieRobinson wrote:

If I'm not getting any air or sounds at all, it's most likely the blower motor, right? And not the control module?

Didn't I specifically tell you to put 12v to the Blower Motor? (not in this write-up) You can do it right in the car without removing it. I've used a Battery Jump Box with some jumper wires before....

Or better yet, get yourself a 194 marker light socket with a bulb. Unplug the blower motor. Put the wires of the light socket into the connector for the blower motor. Turn the heat on HIGH. The bulb should light up BRIGHT. The lower fan speed you go, the dimmer the bulb will get. This would tell you if the BMCM is functioning or not. Or you could use a Voltmeter. 12V being HIGH setting, roughly 6V being LOW, with an even "ramp" in between.

Good idea testing the motor with 12v. Then do the lamp test on the module to rule out wiring/fuse/climate control as issue.

I flew over to Psycho Sexy's hideout today.



Swapped out the BMCM from his parts Riv and sha-blam; air system is back online.

Hi all - my fan in my 97 just stopped working at any speed driving out of the parking lot. Checked fuses, all good. Guy at NAPA whose owned 3 (2 '95s and a '99) said its likely the blower motor or the resistor. He had the blower motor so figured I'd try that first. What a PITA it is taking the blower out without removing the module first! Ah well, live and learn. Ended up having to remove the module anyway as I couldn't unhook the wires from it to let the motor drop. And it turns out, its not the blower anyway. GM module on order from Rock Auto for $120. Thanks for all the writeups - just like to recommend that if anyone needs to replace the blower motor, pull the module first - will make life much easier - cheers!

Guys,
              In case anyone is having a problem with their blower motor speeds, Rockauto is having a wholesaler closeout on on the BWD/Niehoff RU1234, which is the blower motor module for the 98-99 Riviera.  It's only 23.79!  All the other choices are 100.00 or more.  They have 5 left.  I figured what the hell, for 23.79, I'll order it.


I usually leave my climate control on Auto and just select the temperature I want.  I first noticed a problem this past winter as the blower didn't come on when it should have.  Usually when the engine warms up sufficiently, the blower activates and all is well.  This time, it didn't come on until very late and then it stayed on.  As I started using the A/C this Spring, the blower would come on full speed, then quit, and then randomly oscillate between low and higher speeds, then quit, then repeat.  About 5 minutes into my trip, it would stay on, and occasionally quit, then start again.  This solved my problem.  Box says Made in the USA.




https://www.rockauto.com/en/catalog/buick,1998,riviera,3.8l+v6+supercharged,1303322,heat+&+air+conditioning,blower+motor+control+module+/+resistor,6557

AA wrote:

It's a transistor - that appears to work as a motor speed controller for the blower motor. Printed on the component:

M (Motorola)
S141042
MEXICO
9637

You'll need to identify it as NPN or PNP or other transistor type, then match or exceed the rated wattage and provide an equal or better performing heat sink.

I opted to buy the part from a yard for $30 - has lasted over 150k miles so far.

Update -

SJ41042 is the 'industry' part number for this semiconductor. The can is available but price varies wildly. I may try repairing mine if I can dismount it w/o destroying it.

LARRY70GS wrote:

Guys,
              In case anyone is having a problem with their blower motor speeds, Rockauto is having a wholesaler closeout on on the BWD/Niehoff RU1234, which is the blower motor module for the 98-99 Riviera.  It's only 23.79!  All the other choices are 100.00 or more.  They have 5 left.  I figured what the hell, for 23.79, I'll order it.

Aaaaaand they're gone!

1 month short of a year too late. That was a deal.

I just installed a BMCM I pulled from a '99 Aurora today. Was having the intermittent fan full on/fan full off cycling that was said to indicate a dying BMCM. Also, I located sources for replacing the SJ41042. They are cheap (like $2 each) but to get that price I have to buy 6-10 of them ha ha. Also needed is silicone potting compound (the module is sealed with what appears to be dielectric silicone potting compound), it is something like $20 from Digi-Key. If I go forward with rebuilding the BMCM then I will likely post a write-up. Problem right now is kind of stupid - I can't find a spec sheet for the Motorola SJ40142. Thought I might have one in an old ARRL manual, but can't find that manual either. Before doing the write-up I want to check if there is a more readily available equivalent, or an upgrade.

For instance in the write up on the HVAC control head (the dash unit with all the buttons) I mentioned using better power resistors to upgrade the head's resistor bridge. When I re-did mine I used higher wattage/same value/narrower tolerance resistors meant for use in RF applications. The upgrade worked well; I have never had to mess with the resistors again, although I have removed the head twice to replace burned out light bulbs. In the same way, a component for the BMCM with the same functional characteristics but capable of handling more current would be nice, avoiding the failure, since the replacement requires an obsolete component. SO, if any of you happen to have such a spec sheet I'd be much obliged to you for having a look at it.

Albertj

LARRY70GS wrote:

1 month short of a year too late.  That was a deal.

Oops - didn't see how old your post was

Well, the other day, as I was going to work, I noticed the blower motor changing speeds back and forth, and when I shut the engine off, you guessed it, the blower motor kept going. Had to pull the big 30 amp fuse under the rear seat to get it to quit.

Time for another blower control module at 100.00 +

How many have you been through?

Jack the R wrote:

How many have you been through?

Counting the original equipment, this will be the third one. This one only lasted a bit over 3 years. When Rock Auto had the closeout, I should have bought more than one. I didn't think they were this prone to failure.

I'm still on my original AFAIK. I haven't changed it in 16 years of ownership.

LARRY70GS wrote:

Jack the R wrote:

How many have you been through?

Counting the original equipment, this will be the third one.  This one only lasted a bit over 3 years.  When Rock Auto had the closeout, I should have bought more than one.  I didn't think they were this prone to failure.

I wonder if you have an issue in the HVAC control head in the dash.

I am on my 2nd blower module. Changed the first one out for a junkyard unit. I have replaced the HVAC head twice - once for fried resistors and once again for my own convenience in refreshing the lighting.

Original HVAC head here.