A/C Blower

I have a 1998 Chevrolet Tahoe with a blower motor issue. When I turn the fan speed control on the dash I do not get any air out of the vents. After discovering this problem I went down to the blower box and played with the fan speed switch and could hear something toggling or clicking around inside the box but no air and the fan motor did not make any blowing noise. This would lead me to believe that it is not the dash control that has failed. I was wondering what my next step should be to diagnose the problem correctly. Any recommendation or advice is most appreciated.

Need to check for voltage on the purple wire at the fan itself. Also check for a good ground signal on the black wire.

So I went ahead and bought a resistor and blower motor for the job at O’Reillys. Both parts with tax set me back $70.00. I have a lifetime warranty on the blower. I am also picking up a multimeter to test the existing resistor and hopefully isolate the problem. Either way, I think that with both parts in hand I should be able to complete the job today. “Crossing my fingers”. Below is a diagram with instructions to test the resistor. I found those instructions on the internet. Will someone tell me if this description and diagram is accurate? I will be delving into this fix tonight around 6:45. That gives me about 1.5hrs of daylight to work. I’m a newbie to DIY so hopefully that time frame isn’t too ambitious. I will let everyone know how this job goes. Any recommendations on how to get to the parts I am looking at testing / replacing would most appreciated! Thanks

PJE

Are you sure it is the blower motor? I hear the most common problem is the resistors going out.

Check the resistor first:

Pull the connector from the blower motor resistor - as you're looking at the plug with the slots.

The connector looks something like this as you look at it:
________________________________
_____!____!___!______________!____!____!______
!__________________________________________!
!_____!____!______!_____!_______!_____!_______!
!__G__!_F_!___E__!__D__!___C___!__B_!___A__!
!_____!____!______!_____!_______!___ _!_______!!

The letters are to help you with the next part.

E is the ground. Touch one probe to it from your test light or multimeter for each test and follow the order. Each terminal corresponds to a blower setting. You should get about 12 volts for each test with the ignition on,but the engine not running. The blower resistor steps down the voltage to get the blower to spin at the appropriate speed.

A+ E = SPEED SETTING #2
B+E= SPEED #1
C+E= SPEED #4
D+E= SPEED # 3
F+E = SPEED # 5 (HIGH)
G IS HOT AT ALLTIMES YOU SHOULD ALWAYS GET 12 v HERE

If you don't get 12v at each setting, when you change the switch to the corresponding setting and test then the switch is most likely the problem, assuming that the connector at the back of the switch is attached securely and that the wires are in good condition, if all settings get 12 volts when you switch to them, then the blower resistor is most likely your problem.

This gives you enough info to test it, see below to replace it.

The resistor is the more likely culprit...they're known to run hot and fail, but usually when they do you only get one blower speed rather than complete loss of air.

If you're gonna buy the parts before you dive in and time is limited, honestly, I'd first test the blower and connector as suggested before. Then I'd just replace the resistor/switch first rather than bothering with checking with a multimeter or trying to yank out the blower which won't be a quick job. Is the resistor located near the blower or behind the dash? I can't remember, but on my Jimmy it was located with the blower speed switch. Good luck!

Once again check for voltage at the blower motor connector. With the key in the run position go thru each fan speed position.

These voltage figures are just guesses. Make sure you have a good ground connection when checking for voltage.
Low= 6v
Med1=7.5v
Med2=9v
High=12v

If you have voltage as described (guessed) ----Replace the blower motor.

If you don't have voltage as described check and/or replace fuse #12 HTR-AC in the I/P fuse block.

Post back what you find.

The blower motor is located inside the cab passenger side. The resistor pack and blower motor high relay are located on top of the heater plenum close to the tranny hump. Need to take the glove box out for better access.