heater only works in 2 positions!! HELP!!

[angelsairman]

Here i am in North Dakota in the middle of winter and today my heater starts acting up. 1998 S10 4.3 w/AC For a while now it wouldnt switch over to floor and starting today it will only blow air in the 2 or 3 positon. What could this be??? The chiltons manual was far from even coming close to being any help, not even a breakdown of the system. Can someone throw out some ideas and maybe some referance materials!!! Thanks

[gerryff]

Hey Bud, I have the same problem only my fan works in the 1, 2 and 3 position but not in the 4 position. I have changed both the switch and the blower motor resistor but neither solved the problem. Any ideas what else it might be?

[Inze]

I have the same problem with my 96 s-10 blazer my blower motor only works in the 1,2,3 position no high. I replaced the blower motor and this didn't fix it so I took it back out and returned it, then I replaced the dash board blower switch and this didn't fix it so I also returned that, then I replaced the blower resistor relay under the hood on the fire wall next to 2 other relays and this worked, unfortunatley temporarily until it blew again. SO something else is causing the problem. I heard it could be a bad motor or a bad ground but I don't know? I was going to bring it to the dealership this coming monday but I would rather not @ 83$ per hour! Now when I replaced the blower relay under the hood and I accelerated pedal to the metal my interior lights came on and flickered?? SO I guess it's something like a bad ground also when this relay blows it really blows and melts! I SURE HOPE SOMEONE HAS SOME HELP ON THIS. I have been searching this site and with most electrical problems there is no soulution given....

[xtremetrk]

I have a 99 S-10 4-banger and when im stopped 3&4 work but when i have it on 1or2 while im driving it will work because the air from driving forces to blower to move.

[dmbrisket 51]

1 2 and 3 go through a relay and 4 is wide open

[BlazerLT]

for the positions, check for a vacuum leak from the heater controls and valves.

For the fan speeds, 1,2,3 go througha resistor, full power goes through I believe a separate relay.

[xtremetrk]

Where are the relay's and resistors located?

[BlazerLT]

The fuse box in the engine bay if memory serves me correctly.

[Mikado14]

The resistors should be located in the heater box so that the blower will cool them.

[Cam1959]

Originally Posted by BlazerLT

for the positions, check for a vacuum leak from the heater controls and valves.

For the fan speeds, 1,2,3 go througha resistor, full power goes through I believe a separate relay.

my fan stopped working on any speed. i cleaned the ground wire connections. now it works but only in max, not 1,2 or 3.

so i guess i must change the resistors ? i think they are held on top of air box by 2 screws, with 3 or 4 wire female plug connected to their connector tabs ?

[dmbrisket 51]

well first off, kinda an old thread, and second, if cleaning the high ground made the high work try cleaning the intermittent ground (high is controlled on a seperate relay system, same power feed, different ground) and depending on the year it could be a resistor pack or a 'modual'

[Cam1959]

Originally Posted by dmbrisket 51

well first off, kinda an old thread, and second, if cleaning the high ground made the high work try cleaning the intermittent ground (high is controlled on a seperate relay system, same power feed, different ground) and depending on the year it could be a resistor pack or a 'modual'

Sorry and thanks. I was searching to figure out what might be my problem which this thread seems to cover. I am only aware of a ground wire from motor housing screw to fender screw. I'm not sure where any other ground wire would be like you mention for the resistor speeds 1,2 and 3 ?

I'm guessing the resistors are what that multi-wire plug attaches to ontop of air box ?

I don't know where that relay is but it seems relay is okay if only my max speed works ?

[Cam1959]

After reading this informitive thread, I was pretty sure my problem was my resistor module. I am so embarrassed because I had previously wiggled the 4-wire plug connected to resistor module ontop airbox and got no power on speed 1,2,3. I just went to pull-your-own wrecker. Before I went in i decided to take out my resistor pack to take in yard with me. It was hard to pry that plug off. Once off I see the plug female connectors and module male connectors are very rusty. Sprayed with wd40 and scraped the males. Put back on and now all speeds work. Good grief Charlie Brown. I had assumed since wiggling it before, that the connectors weren't the problem.