Blower motor question....a tough one!

Ok...99 Tahoe older body style. Blower motor does not blow. First started to be intermitent then died. Now if it ever comes on its in HIGH only . Tried new motor but it didnt do anything. Tested the leads that plug to the motor...It get power in 1,2,3 settings about 11.xx volts (engine off but higher with it running). The High setting goes to zero on the multimeter. I tried a new relay, didnt work. I put a new dash switch panel in as well. Tried a new resistor, didnt work. The old resistor still looks ok; no signs of burning. So on occasion the motor comes on, but there is a delay from when you turn it to HIGH and when it comes on (maybe 2-3 seconds) and if you turn it off it usually wont come back on. Im stumped since the leads going to the motor are getting power on 1,2,3 settings but the motor doesnt budge. I also bench tested the motor and it runs like a champ off the straight battery. You guess is as good as mine.

Not sure where the ground is for the blower, but I think you want to find it and make sure the connection is clean and tight.

//2000CAYukon

Positions 1, 2 & 3 are powered from the HTR-A/C fuse in the IP fuse block to the resistor pack and then to the motor thru the relaxed contacts of the Blower Motor Relay High. When you go to high the relay energizes and the power to the motor comes from the BLOWER fuse #3 50a in the underhood fuse block. (G202) supplies the ground signal for both the motor and relay and is located "on the right side of the instrument panel, mounted to the HVAC plenum bracket".

'98 C/K service manual.

Ok I tested the blower fuse under the hood with a multimeter when the switch was in the high position; no power unless I ground it to a different source instead of just jumping across the two. So I go test the relay plug and am able to get power on the red to black wire and purple to black. When I jump the purple and red the motor blows full high since it overides the relay. This tells me the relay is not actuating but I have put a new relay on so I dont think its the relay itself. There are 2 other wires that go to the relay (blue and orange I think) and I am guessing on of those sends a signal to energize the relay.

http://www.autoshop101.com/forms/hweb2.pdf might be helpful.

//2000CAYukon

Ok I tested the blower fuse under the hood with a multimeter when the switch was in the high position; no power unless I ground it to a different source instead of just jumping across the two. So I go test the relay plug and am able to get power on the red to black wire and purple to black. When I jump the purple and red the motor blows full high since it overides the relay. This tells me the relay is not actuating but I have put a new relay on so I dont think its the relay itself. There are 2 other wires that go to the relay (blue and orange I think) and I am guessing on of those sends a signal to energize the relay.

The Orange wire is the relay energize signal from the fan switch "high" position. Need to test for a good ground on the black wire from the relay socket and 12v with the key on and the switch in "high" on the orange wire. As far as testing the blower fuse in the underhood box, it is good. That fuse is "hot at all times" and should have power on the red wire at all times. The "dark blue" wire is the feed from the resistor pack to the blower thru the relaxed contacts of the relay. The "purple" wire is the feed from the relay to the blower motor. With the relay "energized" the power is fed thru the relay wires red & purple.

I have a 1996 Tahoe 4dr 4wd,had 10yrs, recently had blower motor problem also strange variation of blower speed problems, long story short take head part out with wires connected, turn key on and fan speed in med, move connector at fan speed connection up/down etc. should start to work ,connection problem at where prongs meet connector , bend prongs to make a better connection ,..solved my problem.