The pictures referenced below are not mine. I "borrowed" them from other Colorado owners postings.
There are three main failures that happen in the blower motor circuit.
1. The contact(s) on the resistor pack burn open or become intermittent.
2. The Splice Pack mounting tab located on the passenger side inner fender gets corroded or rusted.
3. The contact inside the Splice Pack (the black box mounted on the passenger side inner fender) burns open or becomes intermittent.
Other less common problems include:
4. The blower motor fuse 41 (30 amp)
5. The blower motor relay 59 (#8864 or Part number 15328864)
6. The blower motor itself
I have listed the above six items in order of probability. The easiest ones to check immediately are items 4 and 5. Simply open the fuse box under the hood and swap those two items with another of the same size or part number.
Back to item 1, 2, and 3
If the blower motor fails to operate on position 1, 2, and 3 while 4 still works
, then you have a resistor pack problem.
If the motor fails on all 4 positions
, then the resistor pack is probably OK and your problem could be any of the items 2 through 6.
The following assumes your blower motor is failing on all 4 speed positions.
YOU MUST HAVE THE BLOWER MOTOR FAILING TO RUN AT THE TIME YOU DO THIS TEST.
Items 2 and 3 are the ground circuit for the blower motor. To tell if this is your problem, turn the blower motor switch to position 4 (High). If the blower is NOT running, then press the AC button. Look for the yellow light in the center of the AC button. It should be on. If not then press the AC button again. With the yellow light on, turn the blower motor speed switch to the "0" position. The yellow light should go out.
If the yellow light stays on, then you have a problem in the ground circuit which is either item 2 or 3 above.
If the light goes out in position 0, your ground circuit is OK and your failure is item 4, 5, or 6 above. Since you have already swapped item 4 and 5 then it must be item 6 that is failing.
To check item 6 unplug the blower motor and put a voltmeter (or test light) across the blower motor cable contacts with the fan set to position 4. Read the voltage. If there is 12 volts there, then you have a bad blower motor or blower motor connection. Remove the blower motor and as a final check, put 12 volts directly across the motor connector using your engine battery and a couple of jumper leads. This check is to absolutely verify that the motor is failing before you go buy a new one. You could also do this without removing the motor but you will need some long test leads.
I would say your chances are 90% or better that your problem is with items 1, 2, or 3.
Repair of item 1.
This the most common blower motor failure. Disconnect the resistor connector and look at the pins of both the resistor and the socket on the cable.
One of the pins will be burned brown in color.
This is your bad connection that needs to be fixed.
You have several choices:
1. A few people have cleaned up this connection and bent the burned pin (usually pin C) to make better contact and then reinstalled the connector. I do not like this solution because I feel it is not permanent, but if it works for you then fine. You will not hurt anything by trying it and if it fails again you can go to a more permanent solution below.
Insert picture here
2. Replace the resistor and entire cable assembly. These are available as part numbers 15218254 (resistor) and 89019124 cable assembly. There is also a part number for the connector only 15306069. For most people this solution is a permanent fix but a few have reported that the new ones also fail again a year or two later.
Here is a you tube video of this replacement:
3. Replace the resistor and cable end (not the entire cable assembly) In this case the existing cable end is cut off and and a new end is spliced on to the existing cable. These parts are available in the after market from many sources including Rock Auto. GM part number for the cable end is: 15306069
4. On the existing cable cut the connector off of the end and solder the cable conductors direct to the resistor. This is a permanent fix but involves a little more work than the ones above.
I do not know if we have a picture of this, If we do post it here.
Repair of item 2
There is a Splice Pack (SP106) located on the right inner fender. The Splice Pack is a 1.5" square black box with a metal tab sticking out. It is located behind the passenger side of the air cleaner. This connection (G106) to the fender is held by one horizontal bolt with a #10 head.
Remove the bolt and clean the tab with a wire brush until there is no remaining corrosion or rust. Clean the fender around the bolt hole in the same manner. Now put some anti-oxidation grease on the tab and on the fender. Reassemble the splice pack using a tooth type washer between the Splice Pack and fender surface. Anti-oxidation grease is available in the electrical department of Home Depot. Lowes, Menards, or your local hardware store.
Repair of item 3
SP106 (the splice pack) has similar connectors to the resistor pack. The splice pack is the 1.5" square black box removed in item 2 above. Remove the box from the fender and then disassemble the top from the bottom of the box. There are a couple of plastic keepers holding it together. Inside you will find one of the connections burned (pin F) which is brown in color. Remove just that wire from the black box and install a ring electrical terminal connector on it. Now reassemble the box without pin F. Reinstall the box with anti-oxidation grease and a tooth washer and under the same bolt also install the removed wire with the ring terminal on it.
If you need or want a wiring diagram of the blower motor circuit please go here:
That is it. Let us know what you find and please give us the results of the above tests. If you need more help simply ask here. Many, many people here have had to fix this problem so there is lots of experience available here.
Please look here for additional information and lots of good photos: