FAQ: HVAC Blower motor only works part time, or stays on

Hi all... Im a newb here and thought Id contribute a fix I found by an electrical engineer that had an issue with his GM climate control fan controller.

Its a long read and pretty technical but if you have had this problem you know its an expensive fix and the part was poorly designed by GM years ago an has not been upgraded with new parts.

According to this man he has designed the circuit with a better design and better parts to withstand the amp draw of the fan motor.

here is the link to the article:

http://www.autoacforum.com/messageview.cfm?FTVAR_FORUMVIEWTMP=Linear&catid=2&threadid=18909&messid=110317&parentid=110315&ftvar_msgdbtable=

I bought the parts but have not done the repair yet (my big toggle switch works fine for me) the parts were bought from Digikey and were about $20.00.

Let me know if I can help... I think I have the parts list/invoice somewhere. if anyone wants help ordering parts.

Sorry if this has been posted before... did a search and didn't turn up anything.

Jeff Del Vecchio - Pittsburgh, PA

Probably the reason you did not a discussion of this problem, or any interest in this fix, is the Riv (at least the 96- and later Riv) uses a different type of climate control head unit. It has a different configuration, different user interface and very different internals.

For starters, you don't need a Dremel to open it...

Albertj

its not the head unit but the fan controller (mounted in the ductwork) if thats what you mean. Im not sure of the years it was used. there are some different configurations.

thanks

Jeff

jeffyd123 wrote:

its not the head unit but the fan controller (mounted in the ductwork) if thats what you mean. Im not sure of the years it was used. there are some different configurations.

thanks

Jeff

thank you for the clarification. The pictures showed several items including a head unit, however - rereading the articles I see I was wrong.

That said...

1) There is an occasional issue about the dampers that control air flow in the ducts, which you can locate using the [Search] function on this site.

2) Nick D. did a *real* nice job designing a replacement circuit that could be built and serviced in the field. Although looking at the design, I'd think the only mode of field failure would be a dead short with a high current source (e.g. failed fan motor), or a collision that physically destroyed the thing.

3) I also am dismayed at Radio Shack's retreat from the parts business. If it were not for DIgi-Key and for wholesale distributors that seem always to sell as reasonably as they can to cash-and-carry customers who know what they are doing, things would be even more dismal.

4) The Riv climate control fan, in auto mode, is always on--on purpose. I am not aware of problems such as the fan staying on when the system is powered down (the lower left "off" button). For grins, some people have put colored LEDs in to repalce the amber ones - red for off, green for Auto, red for defrost, blue for recirculate I think. Not sure if they select the LEDs for having similar apparent brightness.

Albertj

Ya it is a shame that radio shack did that... but reflects the changing times... actually they almost had all the IC chips except for one which did surprise me.

The fan controls do fail on the cars... they short out and the fan will run constantly even with the key turned off... you have to pull the fuse to stop it.

jeff

On some the earlier GM cars I have personally experienced that problem. Not that much earlier, but a generation of cars before this Gen.
Have not heard of anyone experiencing that problem since being on this board.
I realize we don't represent every 8th gen. Riv owner but there is a good representative quantity of owners on here, whereas if this was a chronic problem we would have a "Write Up' on it I'm sure.
But we sure do appreciate the extra knowledge that the Link to the article provides. It is useful on all GM luxury cars and will prove useful here as well.

I have heard of several blower modulators going bad in riv's. mine went out several years ago. and 2 other local riv owners have had theirs fail as well. maybe the FL heat contributed to their demise, but i seem to recall a few posts on this in the past too. (maybe it was on regalgs IDK)

regardless, thanks for the fix idea!
on a side note, the 95+ rivs do use the same (or very similar) blower motor resistor as mentioned in the article. rockauto has them for $144 at the cheapest! i believe i paid ~$100 a few years ago at the dealer!

My relay is stuck on it won’t shut off the fan; I need to know its location. If it’s the 3 on the firewall, I would like to know which one it is. I’ve looked under the back seat with no luck. I haven't gotten under the dash for longer than to unplug the fan
.
I know it’s the relay because when I turn it on it works fine and does what I ask, but when I shut it off it goes to fan stuck on condition.

Any help would be much appreciated. Thanks.

The '95s use a relay?

Okay, who has a '95 FSM...

Doesnt the HVAC fan run all the time on low speed? I never checked.

Albertj

On my 98 when I turn the HVAC control to OFF, the fan shuts down completely.

But, I think he is saying when he turns the car off, the fan stays running as well.
I'm not sure, need a little more info.

Charlie, have you tried pulling one relay at a time to see if they do indeed shut off the fan. I'm not sure how the 95's are wired either, there are so many differences between 95 and the rest of the years that without the FSM for that year IDK.

Rickw wrote:

On my 98 when I turn the HVAC control to OFF, the fan shuts down completely.

But, I think he is saying when he turns the car off, the fan stays running as well.
I'm not sure, need a little more info.

Charlie, have you tried pulling one relay at a time to see if they do indeed shut off the fan. I'm not sure how the 95's are wired either, there are so many differences between 95 and the rest of the years that without the FSM for that year IDK.

Yeah it does not shut off when i turn key power off, i had to unplug the fan pigtail to get it to shut off. I havn't tryed pulling the 3 under the hood, because my engine was hot when i got home and it didn't feel great on my arms.

I just looked at the schematic for a '95. It appears to NOT have a relay. I just had this happen to me on my '98. It was the Blower Motor Control Module that was shorted internally.

The 3 relays you are referring to under the hood are the 3 fan speed relays. The only other relay in the circuit is the A/C Compressor relay. There is a 30A fuse under the rear seat labeled HVAC BLO MOT FUSE you can pull in order to shut the Blower Motor off.

The BMCM is located on the passenger side (interior floor) "behind" the blower motor. I have pics, I'll do a write-up for you when I get home tonight.....

Unfortunately, it's not a cheap fix. Nobody but the dealer carries that part. It's going to run you about $260 for a 10 minute fix.

I believe our cars use what they call a blower module. It is located behind the glove box. Availability?, not sure.

LARRY70GS wrote:

I believe our cars use what they call a blower module. It is located behind the glove box. Availability?, not sure.

That's what I just said.....except it's on the floor under the glove box.

Abaddon wrote:

I just looked at the schematic for a '95. It appears to NOT have a relay. I just had this happen to me on my '98. It was the Blower Motor Control Module that was shorted internally.

The 3 relays you are referring to under the hood are the 3 fan speed relays. The only other relay in the circuit is the A/C Compressor relay. There is a 30A fuse under the rear seat labeled HVAC BLO MOT FUSE you can pull in order to shut the Blower Motor off.

The BMCM is located on the passenger side (interior floor) "behind" the blower motor. I have pics, I'll do a write-up for you when I get home tonight.....

Unfortunately, it's not a cheap fix. Nobody but the dealer carries that part. It's going to run you about $260 for a 10 minute fix.

Well hell, that sucks i was hoping it was something cheaper. But thank you for correcting me on this one and the info.

Check this link for info on replacement.
https://rivperformance.editboard.com/series-ii-engine-transmission-f4/blower-motor-control-module-replacement-t7381.htm#113780

For what it's worth, RockAuto.com has a Standard Motor Products replacement for the "bargain" price of $150, plus whatever the shipping would be... Traditionally that's a good brand for aftermarket electrics.

Eldo wrote:

For what it's worth, RockAuto.com has a Standard Motor Products replacement for the "bargain" price of $150, plus whatever the shipping would be...

Wow. Didn't know that. I just know that no parts store carries it.....

Are the parts different for 95-99?

1997-1999 uses the same part. The part is unique to only 97-99 Rivieras.

1995-1996 uses a different part, with is also used on 1992-1993 Rivieras, and these other vehicles:

BUICK LESABRE CUSTOM (1992 - 1996)
BUICK LESABRE LIMITED (1992 - 1996)
BUICK PARK AVENUE (1992 - 1999)
BUICK PARK AVENUE ULTRA (1992 - 1998)
CADILLAC ALLANTE (1992 - 1993)
CADILLAC DEVILLE (1992 - 1995)
CADILLAC DEVILLE TOURING (1992 - 1993)
CADILLAC ELDORADO (1992 - 1993)
CADILLAC ELDORADO SPORT 1993
CADILLAC ELDORADO TOURING 1993
CADILLAC SEVILLE (1992 - 1993)
CADILLAC SEVILLE STS (1992 - 1993)
OLDSMOBILE 88 ROYALE (1992 - 1996)
OLDSMOBILE 88 ROYALE LS (1992 - 1996)
OLDSMOBILE 88 ROYALE LSS 1995
OLDSMOBILE 98 REGENCY (1992 - 1994)
OLDSMOBILE 98 REGENCY ELITE (1992 - 1996)
OLDSMOBILE 98 REGENCY TOURING (1992 - 1993)
PONTIAC BONNEVILLE SE (1992 - 1996)
PONTIAC BONNEVILLE SSE (1992 - 1996)
PONTIAC BONNEVILLE SSEI (1992 - 1993)

i hit a bump to hard an ac quit blowing i kicked under dash and worked again and cut car off it wont work again so i kicked it works now well now i kick it and nothing so i take panel loose and hit blower with hammer it worked nice and strong so is my blower bad or something else

This seems like the blower control module is out (common). There's a write-up here:

https://rivperformance.editboard.com/series-ii-engine-transmission-f4/write-up-blower-motor-control-module-replacement-t7381.htm

amaidendevil wrote:

i hit a bump to hard an ac quit blowing i kicked under dash and worked again and cut car off it wont work again so i kicked it works now well now i kick it and nothing so i take panel loose and hit blower with hammer it worked nice and strong so is my blower bad or something else

Shade tree mechanics, homeowner fix-it types, and even astronauts call this "impact adjusting". Surprisingly, it quite often works. You just have to know what size hammer to use. Then, you look carefully to find out why it works. If you are really lucky, it will be something simple and cheap (or no cost) liike a loose wire. Good luck.

Keep in mind that the Blower control module is under there. Might be that and not the blower motor itself.