1997 Pontiac Grand Prix, Bower Erratic, Inop

Hi,

The heater / AC blower motor works erratically. It will not run on any speed except High most of the time.

However, even at "5" (Hi speed setting), it will not start immediately most of the time. If you set it to 5,

it may take 5 seconds or longer to begin running. Even after it is running it will not run at 4 or any lower

speed. Sometimes it did begin to run at a lower speed if you just left it there...it may start several minutes

later but was not predictable at all.

I am an electronics tech so have tried troubleshooting this situation. Initially, I assumed it was going to be

the "resistor" block since it at least always worked at high speed but got to where it never works on the

lower speeds. Then I got to thinking about this failure to start immediately on the high speed. I thought

if the motor "bearings" are getting bad, they may be resisting the startup on the lower speeds to where

it won't run except on high speed (with full voltage).

So I temporarily connected a new blower motor but it behaved the same way... runs after several seconds

of waiting, on high speed only. It doesn't run on any lower setting. I then checked for 12 volts at the connector

with the motor disconnected. It shows about 11.5VDC on the high setting and just a few tenths lower on each

lower setting. (I'm assuming with no load it is not showing the actual voltage drop on those lower settings

that would be normal with the motor connected).

So we know it isn't the motor and also not the resistors since it doesn't explain why the motor still takes

several seconds to start when on High as this should be applying the full battery voltage instantly. With

reading some amount of DC even through the resistors, they should not be an issue nor the series

hi temp fuse.

I noticed a relay "click" each time the blower switch is turned on so assumed it's contacts may be pitted

and responsible for part of the problem. After locating the "box" containing the relay, I noted there were

two other relays on the PC board which also contained 2-3 integrated circuit "chips" . The board had two

multiwire connector blocks which were the connectors for the cabling from/to this assembly.

I'm not familiar with this assembly. I have a "generic" diagram of the blower, switch, and relay but it doesn't show

any other circuitry involved. I'm wondering about the other components on this circuit board and if they are

involved in the function of the blower and it's turning on. I also noted that when the blower switch is turned

on to a low number, you hear the relay click on, but when up to the high setting, it clicks back to off???

Manually closing the relay contact seemed to have no effect on the motor.

So... after all this discussion, what are your thoughts on what is going on here and is this circuit board the

source of all the problem here? Is the circuit board repairable at a component level by myself? If I could get

the part numbers off the IC's, I may be able to change them as there are no other "active" parts on the board

and appears to be nothing overheated/burned.

The numbers found on the "box" with the relays were:

10097889 and 7156J These don't appear to be the GM part numbers and there were no other numbers found

except an insignificant one on the board itself.

Thanks for your support,

Harlan

Hi Harlan,

The first thing to check when the inop condition is power to the three fuses in the right hand fuse box. HVAC Control / 20 amp, HVAC Hi / 30 amp, DIC/HVAC 10 amp. The HVAC Hi fuse should be hot at all times and the other two should be hot with the key on. If all are okay the next step would be to check power and ground at the blower motor itself with all of the harness connectors in place. Let me know what you find and I will provide more info as you test.

Sparky

Hi Sparky,

Thanks so much for your tips. I have a wiring diagram of the circuit in question. After much troubleshooting, I did find the

supply voltage to the blower motor switch was very low to none! It at times would measure around 5 volts. Further checking

at the HVAC control fuse found the same condition at the SUPPLY side of the fuse.

I temporarily bridged that fuse to the adjacent fuse's supply (heavy gauge wire) and everything worked perfectly... all the

speeds of the blower switch functioned as they should. Oddly, with the fuse removed, the voltage on the supply side

would read normal but as soon as the fuse was in and the blower switch on, it dropped to nearly zero.

So the problem now is why and where is the 12 volt supply to this fuse losing it's voltage. There are two lighter gauge

pink wires on the back of that fuse block which carry the supply voltage. I have not been able to locate where they

originate due to the cumbersome wire bundle they run into. Apparently this circuit goes through the ignition switch but

then where does it eventually connect to the battery positive? With the small gauge wire being used (maybe 18-20 gauge..

which seems rather light for running a motor that consumes a fair amount of current) it wouldn't seem likely that much

arcing (corroding / oxidizing) would take place resulting in this condition in the switch.

Also you would think messing with the ignition key and switch position would have an intermittent result where

it would at times work at least to some extent.

If you can find the wiring diagram of how this fuse is supplied and where the supply wires physically run, that would be the

next step and a great help. At least then I could check the voltage at the input to the ignition switch to hopefully rule it out.

BTW... is the ignition "switch" removable from the key function itself... so the electrical switch could be replaced without

requiring a new "key / lock" assembly?

Thanks very much for your time and wading through this mess... been quite a struggle... aching back and sore neck from

crawling around under the dash, etc. :-)

Harlan

Good Morning Harlan,

As you stated in your first email, this has been an ongoing erratic condition that has gotten worse. The ignition switch is your problem as mentioned earlier. To check go to the ignition switch connector at the base of the column. It should make up the center part of a larger junction connection. Check both large red wires for 12 volt supply. If 12 volts is not present check the ignition fuses under the hood. If it is present and it most likely it will be then proceed to check the orange wire for 12 volts with the key on. It will not be there. Next jump the orange wire to one of the red wires and see if the blower now works properly.

The electrical part of the ignition switch can be changed without having to deal with the lock cylinder and key issues. It is fairly simple to change so don't be intimidated by it. You will probably have to invest in some torx bit drivers and sockets in order to replace it if you do not already own them. Any repair manual should show procedure but if you need help just drop me a line.

Sparky,

Hey, Thanks for the speedy reply... sure do appreciate it!

Well suppose it may be the ignition switch then if you're confident

there is nothing else in the "line" that would possibly limit the

voltage the way this behaves.

I don't have the car here now to look into it so will see what happens

when I try the steps you suggested.

Thanks again.. will try to let you know the results.

Harlan

Good Morning Harlan,

As you stated in your first email, this has been an ongoing erratic condition that has gotten worse. The ignition switch is your problem as mentioned earlier. To check go to the ignition switch connector at the base of the column. It should make up the center part of a larger junction connection. Check both large red wires for 12 volt supply. If 12 volts is not present check the ignition fuses under the hood. If it is present and it most likely it will be then proceed to check the orange wire for 12 volts with the key on. It will not be there. Next jump the orange wire to one of the red wires and see if the blower now works properly.

The electrical part of the ignition switch can be changed without having to deal with the lock cylinder and key issues. It is fairly simple to change so don't be intimidated by it. You will probably have to invest in some torx bit drivers and sockets in order to replace it if you do not already own them. Any repair manual should show procedure but if you need help just drop me a line.

Sparky,

Hello again,

After further troubleshooting, I did conclude as you suggested, the ignition switch is the entire

problem. I've never had this part of a car apart before so it was a bit challenging to get at the

switch area on the steering column. Managed to have something close to the necessary tools

to do the job but sure was a lot of work.

Another thing that made it more difficult was that the wiring harness to the connector block under

the dash needed to be reworked. I had tapped into about 5 wires some time ago when installing

a remote car starter. So I had to get that all out on the bench and splice those lines back into

the new wiring harness. Yes the switch is apparently only available with it's attached wiring

harness with black plastic connector block.

Well this has been a difficult one since I was hoping it would only be the blower motor at the

beginning but was really the ignition switch... can't wait to tear it apart and see what contacts

look like to cause this trouble. Also left in the new blower motor as it occasionally would squeal.

Thanks very much, Sparky and have a great day!

Harlan