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Blower resistor location

08-12-2004, 12:42 PM
I have read in some posts that the blower motor speeds are controlled by resistors that occasionally go. I had one replaced under warranty so I don't know how to get at them. How do you get at the resistors? I assume that they are under the dash but how do you take it apart to get to them?


08-12-2004, 02:20 PM
This is one of those problems that could be a couple of things. A lot of people replace the blower motor resistor and it fixes that problem. I have done this and it is moderately easy with a $40 part from the dealer. However, this did not fix my problem.

Then there are other people, like myself, who had to replace the ignition switch harness to fix the problem. The primary difference in the symptoms I saw with this problem versus others was that my headlights would go off when I selected a "bad" fan setting. Also, some of the lights near the fan now would freak out, like the AC light and the defrost light. This fix is more in depth and requires removing a lot more parts around the steering column and under dash. The part is ~$100 from dealer or about $60 online. Good luck.

Blower motor resistor

And here is how to change this little bastard :biggrin: . Remove the underdash panel on the pass. side. There are three push tabs that hold it in. At least on a 97 GTP. Ok you have the panel off. Set that somewhere you will not foget it.
With your head in the floor look torward the firewall. The blower resistor is mounted in the bottom of the HVAC ducting. Unplug that harness that attatches to it and move it out of the way. Now take a 5.5 mm socket and remove the blower motor. Once that is down and the plug is disconnected, set that aside. If you have bought the blower resistor, then you will know kinda what to look for. You can see two of the three 5.5mm bolts that you need to remove. Remove the easy one. That is the closest one to you. Somewhere in here you will need to be on your back, head into the center console, and cussing cause you're not left handed. Next unbolt the remaining bolt that you can see. It may not unbolt all of the way because the sound deadener is in the way. Here is the choice. Use a knife and cut it, or just unbolt it was far as you can. For the last bolt, it is hidden behind a plug connector. You cannot get to that one without cutting the sound deadener or breaking the blower resistor. I chose to break it cause did not work anyway. I got it out. Not too bad. To make it easier to get the new one in, loosen that last offending screw a turn or so. I put a light coat of silicone on the new piece to seal it well since I would not be able to turn that back screw.

Installation is the reverse. Before you button it all back up, make sure the blower works.

Also here is a post from another person on how to replace the Ignition switch harness

Ignition switch harness let?languagecd=EN&countrycd=US&user=InternetUser&mfgname=ACDELCO&prodlinecd=1&acpartnbr=D1490D
I have a '97 GT that I bought new, so I've had my car on the road longer
than most of those in this group. That being the case, one can reasonably
expect equipment failure to show up sooner on my GP than on newer models.

One interesting failure is something called the "fan ignition switch." That
switch is a thick cluster of heavy and lesser wires, about 1.5 feet long,
with robust termination blocks on each end. One end also has geared,
mechanical components. This part installs under the dash on the drivers
side and up into the steering column.

You need to replace it when your A/C fan begins to operate intermittently.
For example, if you are driving and the fan simply stops, then restarts
while on any speed setting 1-4 (not on speed setting five setting until some
weeks later ,) your switch is failing. The problem will gradually become
worse, with the outage taking longer to recover, until you achieve total

There are actualy two parts that can cause this problem, and the second part
is called the resistor pack. That part connects directly to the blower
housing under the dash on the passenger side, and is about 24 bucks new from
GM. My fully functional pack was slightly burned on the circuit board, so I
replaced it.

The fan ignition switch was easy to replace, but it is awkward to install.
You will need typical small hand tools, plus an 8-inch or longer socket
extension. a torx male socket (T11, I think) and two torx female sockets
(T11 and T10.) I didn't know that until I had my steering column torn down,
and had to drive around the city with a skeletal column, wires dangling and
tools in the floorboard. No one sells female torx wrenches that small, so
you will have to buy two small standard wrenches. (Your 1/8th inch drive
sockets are way too big to fit the space you will have to work with.)

Sears has a perfect solution. Buy the 5/32nd and 1/8th size wrenches on the
2.5 inch steel stems. They look like small screwdrivers with the socket
permanently mounted at the end of a thin, steel stem. You will need the
small stem because you won't be able to remove the cowl above the steering
column, and its in the way.

The physical key slot on the primary ingnition switch is too big for the
upper steering column cowl to slide over, so you will have to raise the
plastic cowl as far as possible to access the two very, very small torx
screws holding the fan switch in place. The cowl will be stressed, so be

Also, you will have to cut and splice two wires due to being unable to
remove the upper steering column cowl. There is some magic part snapped
into a slot on the top of the column that you will not be able to reach,
which will have to be left there. Cut the two wires coming off it and
splice them to the two matching wires coming off your new part. There is a
small, odd shaped white plastic box attached to one end the two wires.
Nothing comes out of the little box, and there are no metal contacts on the
surface of it. Apparently, there is something inside the box that sends
some kind of signal/magnetism/charge through its housing to a receiver in
the steering column. Or not. Who knows?

The wires are very plainly marked, they match the new ones and there are
only two. You can't screw it up unless you fail to insulate your splices.
If you don't unsulate them well, then you can expect some really fun
problems later, and maybe even some fireworks in your lap as you drive down
the highway, impressing your woman with your technical prowess :)

That job takes about 1.5 hours, and the part is 56 bucks from Grand. GM
wants 98 dollars for it, and a shop will charge you around 300 dollars to do

Just to add to his directions, to get the top cover off, put the key in the ignition and turn it to START (disconnect the battery first!), and then leave it. Push a small allen wrench in the hole above the ignition switch, and you can pull the whole thing out. Then you can remove the small white thing, which has a button on it, and controls the key alarm that tells you when you've left your keys in the ignition. The tip about the Sears tools is definitely a life saver. The 2 driver's you need are:

Craftsman Professional 1/8 x 2 1/2 41865
Craftsman Professional 5/32 x 2 1/2 41866

They're $2.99 each

Sorry for making this so long,but im sure if others use the search it will come in very handy :wink:


09-25-2004, 10:15 AM
Thanks to BigL for his comments regarding the possible causes of the blower motor only working when speed 5 was selected. I had the same symptoms with my 97 GP.

I replaced the heater resistor first. It's not really that bad to change as the two rear screws at the back that are hard to get to only need to be loosened, not removed. The holes in the resistor mounting plate are slotted, so when the back two screws are loosened and the front one removed, it slides out easily.

Unfortunately that didn't fix the problem and I was sceptical about replacing the ignition switch to fix a blower problem that affected the daylight running lights. Especially considering it cost $260 from the dealer in Canada. As GM listed 16 different switches for that year, I figured the dealer was the safe way to go.

I started the job myself, but as mentioned by BigL, the female torx sockets are a must to get the top cover off the steering column. As I could find none in town, I ended up taking the care to a local shop to finish the job for me.

It was worth it in the end as replacing the ignition switch c/w wiring harness did resolve the problem of the blower not working on fan selections 1-4.

Thanks for the help.

09-25-2004, 10:37 AM
Im glad the post worked out for you....Im hoping that this post will help others with the fan problem,as most people always think that its the blower resistor.A good way to not mess up the harness again, is to make sure you always turn the fan switch off before shuting off the car.That way there is no voltage spike to the contacts and that is what is so hard on them causing that problem over time.

Take care

09-25-2004, 11:16 PM
$40 part!!!!? my dealer was gonna sell it for $20 plus tax.

10-03-2004, 11:09 AM
BIG-L provides a wealth of information here to fix the blower problem. I changed my resistor recently and then the ignition switch yesterday.

A must have tool to change the resistor is a flexible socket extension. it can be purchased at Sears. instead of a solid rod type extension it is flexible like a spring. You can guide it to the hidden screws on the back side of the resistor module to loosen them, do not remove them completely.

In regard to the ignition switch here is the step by step of what I did. First you will need the two small nut drivers mentioned by BIG-L above from Sears. My local Sears had discontinued them and only had the 5/32 and I could not find them anywhere else. I estimated that the male torx head of the screw was equivalent to a T-20 torx bit. I found a T-20 torx deck screw and the male screw head fit the female screw head perfectly. I had a piece of 1/4" stainless steel tubing and screwed the torx screw into the hole in the end of it. I bent the other end to form a handle and used it as a wrench to remove the screws. If you don't have tubing available probably copper tubing or a wood dowel rod would work as the wrench handle. Another must have tool is a mechanic's telescopic mirror. This tool will allow you to see around the back side of some of the electrical plugs and aid in the removal of them with out having to get in awkward positions to do so.

Ignition switch removal on a 1998 Grand Prix with tilt steering:


Look inside the slot where the tilt steering knob is located. There is a black metal piece where the knob inserts into the tilt mechanism. Pry it back slightly with a small screwdriver. One from an electronics tool set will work. While you have it pried, pull the knob out and it should release.

Remove the two screws from the bottom of the steering column cover and remove the cover.

Remove the two screws that hold the top steering column cover in place.

Insert the ignition key into the key cylinder and turn the key clockwise to the start position. Nothing will happen because you have disconnected the battery prior to starting this project. Lift the top steering column cover being careful not to break it because it is still held in place by the ignition key cylinder. You will see with your mirror near the back end of the cylinder housing a small hole. Stick a small allen wrench in the hole, this will release the key cylinder so that it can be pulled out. Once the key cylinder is removed the column top cover is free to be removed.

The black box below the key cylinder with all of the wires coming out of it is the ignition switch that you are changing. Look at the switch you have purchased for this repair. Notice that the small white plug with two wires attached has a tab on the side that can be pushed down, this is the release for the plug-in. Using your mirror you will see that plug-in against the ignition switch housing where it plugs in. Using a small screw driver press the release tab in against the plug and rotate the plug 90 degrees to the right to remove it. To do otherwise may break the plug.

Remove the plug from the white key release device by inserting a small screw driver and pressing the release tab on it.

Undo the two screws holding the ignition switch.

Undo the plug at the opposite end of the ignition switch by unscrewing the bolt in the center of the plug and unplugging it.

There is a black wiring plug on top and a gray one on the bottom of the ignition switch plug that need to be removed. This is done by prying the center of the plug case where it meets the ignition harness plug while sliding it forward.

Cut any tywraps holding the wire harness in place and feed it out of the dash.

To install do the reverse of the above, and tywrap the new harness into place. Be sure to properly align the key cylinder when replacing it in the housing and if the key will not come out of the cylinder there is a silver key release button at the bottom of the white device in front of the ignition switch. Press it and the key will come out. Also when replacing the ignition switch make sure that the slot in the switch is properly aligned with the corresponding part on the steering column that fits in the slot.

10-03-2004, 12:16 PM
Hey Marty,if you wouldnt mind may be you could copy and paste your write up to this link.That way we might try and keep this information all together...By the way nice write up!

10-03-2004, 07:03 PM

Thanks for the original post I never would have figured this problem out. That's a nice looking Grand Prix you have. What do you wax it with?
I used to use Zymol but tried 5 Star Shine last week...that suff is amazing, dirt will not stick to the finish after using it. If you are not familiar with it check it out at

I will copy and paste my comments to the other link.

Thanks again.

10-26-2004, 12:38 PM
What do you wax it with?

Sorry I didnt answer this before.

Thanks for the compliment.I use BlackFire, its a 2 step process and it has no wax in it.Its made for red or darker colored cars and it is the best ive ever used and belive me ive tried alot of stuff thru out my 32yrs of owning cars :wink:

10-26-2004, 01:52 PM
I have a 97, and heater quit on wife yesterday..It had been squealing when starting for a while, so I think blower is shot..also a few months ago battery was completely dead one morning, when I charged it up, found heater to be running on high even with ignition in off. Found that by removing high speed fuse blower quit and no more dead battery but also no high on fan even though other speeds worked well till now. My question is what else is wrong along w/blower, is there a relay in there that needs to replaced?

10-26-2004, 03:18 PM
My question is what else is wrong along w/blower, is there a relay in there that needs to replaced?

Sounds like the contact in the ignition switch harness has stuck closed.That would be the reason for the fan to be on high when the ignition is off.

Time to replace the harness.


10-26-2004, 05:42 PM
Well I got the ole b---- apart, blower still works on bench but is about shot, rust on inside and squeals when it starts, blower resister is shot, came out in pieces, and is all burnt up...will replace these and try, hope I don't have to do harness..I'm goingto say a little prayer...Thanks for the help...

10-26-2004, 06:58 PM
Keep in touch and lets use know how things go!


12-20-2004, 10:09 AM
Hey Big-L, I was at the dealership today for the same problem you described. Sometimes if I turn it below 5, all the lights go out, dash, headlights, defrost goes screwey. Of course they found nothing wrong with the car and said bring it in when its doing it thats going to happen.

Of course they had to repeatedly tell me how in 20 years they have never heard of this happening and how HE owns a 99 and never had this problem. well gee, I guess if youve never heard of it and your car doesnt do it, then Im just making it all up *rolling eyes*

thanks for the post, Ill pass it on to my husband!

12-20-2004, 10:30 AM
You know every dealer owns the cars they sell, ya right.
They work on them all day long, they know all the troubles that they have on them. Why would they own them.

12-20-2004, 04:43 PM
Hey Big-L, I was at the dealership today for the same problem you described. Sometimes if I turn it below 5, all the lights go out, dash, headlights, defrost goes screwey. Of course they found nothing wrong with the car and said bring it in when its doing it thats going to happen.

Of course they had to repeatedly tell me how in 20 years they have never heard of this happening and how HE owns a 99 and never had this problem. well gee, I guess if youve never heard of it and your car doesnt do it, then Im just making it all up *rolling eyes*

thanks for the post, Ill pass it on to my husband!

Im glad that some of my post are helping other's in the GrandPrix community. :bigthumb:

Ive found that if you turn off the fan before starting the car,there wount be such a voltage spike in the Ignition Harness/Contacts and some might be able to keep the harness lasting a bit longer.


12-22-2004, 12:41 PM
Hey there everyone that is having the problems with the blower resistor this link might just help you fix it yourself.

01-11-2005, 12:26 PM
Is there any way to test if the ignition harness that you write about is really bad? I have a 98 Grand Prix and it sounds like the same symptoms, but I'd like to test before trying to replace, if possible.

01-23-2005, 10:56 PM
Good day, our car vibrates like hell when we turn the heat past 3.... and then low and behold today when its minus 27 celsius the only setting on our instrument panel that works is #5. Through research I see the problem is most time associated with Blower Resistor part #ru60. But what about this wicked vibration? Woould it be best to replace the entire blower motor instead of just doing the resistor??

To all those who post thanx very much, I hope to save some $$$ doing job myself in the balmy Canadian air! LOL :naughty:

01-23-2005, 11:15 PM
The above link doesn't work, can you repost one that does?

01-30-2005, 08:12 AM
I started experiencing the no fan at settings 1-4 and only working on 5 issue on my 99 Grand Prix GT. If I turned to a bad fan setting, the motor would stop blowing. When I went back to 5, I would have to mess with my temp control knob to get it to come back on. I also noticed that my headlights would turn off on the bad settings. According to Larry's post, this meant that the ignition harness had gone bad. And he was right. I tried a new resistor pack first but that didnít fix it. I did install a new resistor pack anyways because the green coating on the factory resistor PCB had gotten very hot and had begun to peel off. I figured no point in ruining the new harness if the resistor pack decides to go. And there's the potential fire hazard if something were to contact the hot, exposed resistors.

Here's how I troubleshot:
I pulled the connector off of the resistor pack and tried measuring voltages at different fan settings. I placed my negative lead on Pin E. It has a black wire so I'm guessing its ground. I had 12V on pin G. I cycled through each fan setting and measured every pin at each setting. I was getting 0V on all pins except Pin G, which had 12V on all settings. This told me that the harness was probably bad. I went and purchased the harness, resistor pack and nutdrivers. I connected the new resistor pack to the motor without mounting it. The motor would only work on 5 so I went for the ignition harness.

Ignition Harness Removal from the steering column:
Disconnect the negative terminal from the battery.
Remove the lower panel on the driver side that has the 2 plastic push locks and a light.
Remove the 2 screws that secure that lower steering column cover. Pull the panel towards you and the clips at the top should release.
Remove the tilt lever by pulling it out towards the door. (There might be more to it but thatís all it took on mine.)
With a #20 Torx, remove the 2 screws that hold the steering column lower shroud. The shrouds have two tabs in the back that interlock them together. Pull the front of the shrouds apart and then maneuver the lower shroud back to get it to unlock from the upper.
Using the 5/32" Micro-tech nut driver, remove the 2 male Torx screws that hold the upper shroud.
Get the upper shroud's lip out of the steering wheel and gently tilt the upper shroud back towards the gauges.
Locate the small hole in the metal cylinder where the key cylinder is. Note: These parts are located under the shroud.
Make sure the battery is disconnected. Insert the key. Turn and hold the key to START. Then insert a 1/16" Allen Wrench into the small hole on the metal cylinder. There should be slight click sound. Remove the allen wrench and turn the key back to RUN. This releases the key cylinder. You should be able to pull it out very easily, jiggling it slightly.
Remove the upper shroud.
Locate the connector on top of the metal cylinder. Insert your finger in the key cylinder and depress the white switch. Turn the connector clockwise and it should pop out.
Remove the connector on the while plastic cylinder.
Using the 1/8" Micro-Tech nutdriver, remove the 2 male Torx screws that hold the switch portion of the harness.
Work the harness back through the opening. You may need to cut some tie-wraps along the way. Keep track of the harness routing.
Loosen the center bolt on the other end of the harness, which is located under the dash.
Pull the harness out. You will need to remove two other harnesses from this one. Note where the harnesses go. They are keyed so they should only go in one way.

Installation: Reverse the process. You may need to reinsert the key and cylinder and turn it back to OFF to get the new harnesses switch hole to align to the plastic pin in the steering column.

After I installed the harness, I tested the voltages on the resistor pack cable again and here are the voltages:
Voltages at Fan Settings
Pin Fan Setting
Off 1 2 3 4 5
A 0 0 12 0 0 0
B 0 12 0 0 0 0
C 0 0 0 0 12 0
D 0 0 0 12 0 0
E Ground
F 0 0 0 0 0 12
G 12 12 12 12 12 12

The part numbers for these 2 parts are:
Ignition Switch Harness AC Delco D1491D GM# 26068757
a.k.a. Ignition Starter Switch
a.k.a. Switch Commutateur Interruptor
Price: $64 online - $116 GM dealer

Blower Motor Resistor AC Delco# 1580571 GM#89018643
Price: $25 online - $38.50 GM dealer
Note: The AC Delco unit looks better built that the flimsy factory resistor pack PCB.

Tools Needed:
Craftsman 1/8" Micro-Tech nutdriver Sears# 41865
Craftsman 5/32" Micro-Tech nutdriver Sears# 41866
#20 Torx male screwdriver.
Phillips #2 screwdriver
Wire cutter to cut tie-wraps
1/16" Allen Wrench
5.5mm Socket, universal joint and some extensions for your ratchet size if you are going to remove the resistor pack.
A multimeter.

Sorry this is so long and a repeat, but I figured I would add some details that I wish I had known while I was working on mine. Of course, if something doesn't work for you in this post, read the rest to see if you can find the answer.

Thanks to Larry and everyone else for the info. It made this problem easy to diagnose and repair. I was glad to see I'm not the only one with this problem. But it also points out a defect in part that shouldn't go bad. All of this because you leave your fan on when turning your car on and off.


03-12-2006, 08:24 PM
hey there big L and every1 else with the heater problem. I guess I have much the same symtoms. That is the switch won't work on 1-4 but does on 5 and if 1-4 IS selected the headlights go out if the DRLs are on. I guess what I am wondering would it be best to change the ignition switch and not the resistor, or to maybe do both? Any sujestions from people more experienced in this problem would be great. ( 1998 GT )

03-13-2006, 08:31 AM
hey there big L and every1 else with the heater problem. I guess I have much the same symtoms. That is the switch won't work on 1-4 but does on 5 and if 1-4 IS selected the headlights go out if the DRLs are on. I guess what I am wondering would it be best to change the ignition switch and not the resistor, or to maybe do both? Any sujestions from people more experienced in this problem would be great. ( 1998 GT )

This is an old post and message thread over one year old and not a good idea to bring up a post this old. It is highly recommended to post your problem in a new post for more visibility and better assistance.

Notification sent to forum Moderator (GTPDad).

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