1999 Tahoe blower fan problems

In the last year.....
My heat/AC blower fan began intermittently stopping, no matter which speed was selected on the switch. Usually it would not come on until I got moving and hit a few street bumps. And, a tap or so on the under-dash plastic housing would almost always get it going.

Then, I lost the high speed setting entirely about 3 months ago, with the other lower fan speeds continuing to work using the above procedure.

A couple of weeks ago, it stopped working altogether, and no amount of banging on it would help.

After reading a lot online, I blew $20.00 today on a new relay, the one next to the resistor block above the housing. I thought it controlled the high speed setting. No change. I did partially remove and examine the resistor block, and visually it looks OK....nothing scorched or burned)

(Interestingly, with all the fooling around under the dash today, it has started working again on the lower speeds only. I'm sure that is only temporary.)

Does getting it to work by banging on it mean the brushes are about shot in the motor?

Can the resistor block have anything to do with the high speed setting?

Can anyone tell me where to go next?

Also, I've gotten conflicting info on the cabin air filter. Does my '99 have one?

Many thanks for any help or direction.

In the last year.....
My heat/AC blower fan began intermittently stopping, no matter which speed was selected on the switch. Usually it would not come on until I got moving and hit a few street bumps. And, a tap or so on the under-dash plastic housing would almost always get it going.

Then, I lost the high speed setting entirely about 3 months ago, with the other lower fan speeds continuing to work using the above procedure.

A couple of weeks ago, it stopped working altogether, and no amount of banging on it would help.

After reading a lot online, I blew $20.00 today on a new relay, the one next to the resistor block above the housing. I thought it controlled the high speed setting. No change. I did partially remove and examine the resistor block, and visually it looks OK....nothing scorched or burned)

(Interestingly, with all the fooling around under the dash today, it has started working again on the lower speeds only. I'm sure that is only temporary.)

Does getting it to work by banging on it mean the brushes are about shot in the motor?

Can the resistor block have anything to do with the high speed setting?

Can anyone tell me where to go next?

Also, I've gotten conflicting info on the cabin air filter. Does my '99 have one?

Many thanks for any help or direction.

2 posts since 2003 ? interesting !

with the new body style you have 2 filters side by side that fit in a slot about 2 inches from the blower motor.

your problem may indeed be the blower brushes worn or sticking. remove the motor using small jumper wires run blower directly with the 12 volts ..see if this then cuts out..If you have alot of miles like 190,ooo and run the blower on high speed often it most likely would be the motor.

if both the high speed and resistor lower speeds all fail this can also be the fuses loose in the sockets

Also, I've gotten conflicting info on the cabin air filter. Does my '99 have one?


Need to tell us if your '99 is OBS (Old body Style) or NBS (New Body Style).
OBS looks like a '97. NBS looks like an '01.

Lot's of electronic differences between the two.

Its the old body style. Thanks.

99% sure there are no cabin filters on the OBS.

1st thing is to check for power at the blower in all positions. The voltage will be lower in the 1st 3 and then should show a full 12v in high. Also check for a good ground signal at the blower.

The resistor pack is bypassed in high.

Check "HTR-AC" fuse #12 in the IP fuse block. Check "BLOWER" fuse #3 in the Underhood fuse block.