Need help troubleshooting front blower

Hi everyone,

Replaced blower motor on my 1999 Astro van during the first week of February 2012 because I heard squealing and figured the motor was going bad. Our van has the knob with 4 blower positions. After I changed the blower motor, it worked on the first three positions (the 4th position hasn't worked for years - wife never used it because it was too loud for her). On a trip to California, the blower started acting up and worked intermittently and finally stopped completely.

After doing some reading on the forum, I think I either need to replace the blower motor again (lifetime warranty from autozone) or change the blower resistor. Before I pull out the blower motor, is there a way to check it? Do you think the motor would go out that quickly? Is it the blower resistor? I've read some posts by old_master about burned out connector plugs and bypassing relays so I'm not sure what steps I should take first for troubleshooting.

Thanks in advance

Turn the ignition to the RUN position.
Select HEAT on the HVAC mode switch.
Unplug the blower resistor/relay pack connector on the front of the evaporator housing, next to the AC accumulator, (large aluminum "can").
At the electrical connector check the following:
Yellow wire must show battery voltage with blower switch in the LOW position.
Tan wire must show battery voltage with blower switch in the MED 1 position.
Light blue wire must show battery voltage with blower switch in the MED 2 position.
Orange wire must show battery voltage with blower switch in the HIGH position.
Red wire must show battery voltage at all times.
Black wire must show less than 5 ohms resistance to ground at all times.
Purple wire goes to the blower motor.

Post your results for each wire.

Turn the ignition to the RUN position.
Select HEAT on the HVAC mode switch.
Unplug the blower resistor/relay pack connector on the front of the evaporator housing, next to the AC accumulator, (large aluminum "can").
At the electrical connector check the following:
Yellow wire must show battery voltage with blower switch in the LOW position.
Tan wire must show battery voltage with blower switch in the MED 1 position.
Light blue wire must show battery voltage with blower switch in the MED 2 position.
Orange wire must show battery voltage with blower switch in the HIGH position.
Red wire must show battery voltage at all times.
Black wire must show less than 5 ohms resistance to ground at all times.
Purple wire goes to the blower motor.

Post your results for each wire.

Old Master- Thanks for all your information on the front blower as it has got things going for me--I replaced the pigtail as well as the resistor last year and all was well until today--I obtained a used pigtail that looked to be in very good shape and bought a resistor new from e-bay--I had two major meltdowns at the pigtail connection again and recently ordered a new pigtail and resistor---is there something that can be done to fix the melting issue---could it be a bad relay?

What were the wire colors that melted?

What were the wire colors that melted?
It seems it is the Large orange wire all the way to the left and the large black one as shown.

http://s1186.photobucket.com/albums/z365/tiletrader/?action=view&current=100_0274.jpg

Excessive resistance causes wiring to burn. The problem is in the ground circuit for the motor, or the motor itself. The relay inside the resistor assembly is carrying the current just fine, that's why the orange wire burned.

Check resistance from the black wire at the blower motor, to battery negative. It must be less than 5 ohms.

Unplug the electrical connector from the resistor:
Black wire to battery negative must be less than 5 ohms.

Post your results.

Excessive resistance causes wiring to burn. The problem is in the ground circuit for the motor, or the motor itself. The relay inside the resistor assembly is carrying the current just fine, that's why the orange wire burned.

Check resistance from the black wire at the blower motor, to battery negative. It must be less than 5 ohms.

Unplug the electrical connector from the resistor:
Black wire to battery negative must be less than 5 ohms.

Post your results. Will Do--You are talking about the black wire coming off the blower motor itself? The blower motor is fairly new as I changed it when I had everything out last time---I will get it done as soon as these storms pass and post

Yes, black wire where it attaches to the motor. If you replaced the motor and are still having the same problem, it's probably a poor connection where the black wire attaches to the body.

Yes, black wire where it attaches to the motor. If you replaced the motor and are still having the same problem, it's probably a poor connection where the black wire attaches to the body.
Have not had that problem until I change the blower motor--The iisue before was on the original resistor and motor and only involved the large orange wire on the far left--Thats one reason I was a bit surprised when I pulled the pigtail off and saw the black wire in the condition it was--I will do a little testing and post the results--My new pigtail and resistor not due in for a few days. And of coarse the replacement blower motor was certainly not AC/Delco...

Have not had that problem until I change the blower motor--The iisue before was on the original resistor and motor and only involved the large orange wire on the far left--Thats one reason I was a bit surprised when I pulled the pigtail off and saw the black wire in the condition it was--I will do a little testing and post the results--My new pigtail and resistor not due in for a few days. And of coarse the replacement blower motor was certainly not AC/Delco...
My Ohm setting on the multimeter simply says 1 - no matter what setting I have it on--Ran a jumper wire from the battery negative to probe and tested the black wire with the other probe---what am I doing wrong

What reading do you get if you touch the probes together? Should be zero. Some multimeters will show "1" or "over range" if there is an open circuit. If the reading is correct, ("1"), this is the reason the wires burned, and you need to run a new ground wire to the motor.

What reading do you get if you touch the probes together? Should be zero. Some multimeters will show "1" or "over range" if there is an open circuit. If the reading is correct, ("1"), this is the reason the wires burned, and you need to run a new ground wire to the motor. I installed a new harness and resistor and tend to agree on running the new ground wire to the motor. I'm thinking running the new ground wire to one of the common grounds on the firewall should do nicely---the last thing I want is a repeat after soldering in a new harness and installing a new resistor pack. I got all AC/Delco parts although it wasn't advertised as such--Harness not color coded so re-wire could easily be messed up if not careful. Also - There is a fuse that controls the high speed only in the front fuse compartment under the hood---the fuse that controls the other speeds is located inside van under the dash---These need to be checked when having issues---also always unplug your battery before attempting to change harness and resistor---if you don't a fuse will pop for sure at the very least.