Blower Motor only works on High

[GM Line Rat]

Hi, 1st post in this forum...99 S-10 2.2 4 Banger/Auto Trans. Trucks getting Heat with no problem but the blower motor is only working on the highest speed. My 1st thought was the blower motor resistor pack under the hood. Cant find a wiring diagram for this circut in my haynes manual.... . I removed it and checked for Voltage using a 12V test light.... Key on, engine off, 12V's present at the orange wire, no visable oxidation or rusting on any teminals in the resistor pack but I still suspect it's the culprit....Only other thought would be a bad blower motor speed switch in the heater control head?.....Any idea's......Thanks for any help!

[old_master]

I would suspect the high blower relay is faulty. All blower speeds go through the high blower relay. The normally closed contacts in the relay handle speeds 1, 2, & 3 from the blower resistor. When high speed is selected, those contacts open and connect battery voltage to the blower motor through the other set of contacts.

[GM Line Rat]

Where is the high speed blower motor relay located at on this 99 S-10 Truck?......Thanks

[Blue Bowtie]

Look in the very front (rear?) of the glove box. I believe it is still there on the '99 models.

There is a 50/50 chance it's the relay or the resistor. The relay is easy to swap to find out. The blower resistor is easy to diagnose with a voltmeter by backprobing the connector with everything plugged in.

[GM Line Rat]

Pulled the glove box out last night but the only relay I find behind it is the Turn signal/Flasher relay....Odd place for that to be? It's usually below the steering column???.... I have a fluke multimeter to check the DC Voltage for the resistor pack and I'll locate the relay location on this 99 S-10 truck tonight......Thanks for the info.....I'll post back with the fix!

[old_master]

Trace the wire starting at the blower motor, it goes directly to the high blower relay.

[DHWest Bend]

Originally Posted by GM Line Rat

Hi, 1st post in this forum...99 S-10 2.2 4 Banger/Auto Trans. Trucks getting Heat with no problem but the blower motor is only working on the highest speed. My 1st thought was the blower motor resistor pack under the hood. Cant find a wiring diagram for this circut in my haynes manual.... . I removed it and checked for Voltage using a 12V test light.... Key on, engine off, 12V's present at the orange wire, no visable oxidation or rusting on any teminals in the resistor pack but I still suspect it's the culprit....Only other thought would be a bad blower motor speed switch in the heater control head?.....Any idea's......Thanks for any help!

It may be where it is on my 94- just to the right of the blower motor on the firewall (standing in front of the truck). I had the same problem and the resistor assembly replacement fixed it.