This is a very common problem on 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 and 2007 Chevrolet Silverado and GMC Sierra trucks. Over a period of time the resistor and usually the connector overheat and blower operation stops in some or all speeds.
The blower resistor is located on the passenger side of the vehicle behind the glove box. There is a plastic cover that has to be removed to gain access to the resistor and wiring.
After the cover is removed disconnect the harness connector and inspect for damage. On this particular vehicle the only terminals that were damaged were the third from the right and the third from the left. Sometimes all of the terminals will be damaged and the plug will be melted to the resistor as shown in the last pictures.
After thoroughly inspecting the connector for damage the terminal retaining comb was removed from the old and the new harness connectors. The good wiring was transferred one at a time from the old connector to the new connector. A terminal extracting tool is needed to do this. The locking tab must be slightly depressed before the terminal can be removed from the connector. A solid piece of wire such as a larger paperclip could be used if a tool is not available. If you do not have an adequate tool or experience this should not be done. Cut the wires one at a time and splice in to the harness using a quality butt connector.
Be sure to stagger the spliced connectors as much as possible in order to have a neater and less troublesome repair.
Retape the harness and install the new blower resistor and harness connector. As with any wiring repair that involves a burnt connector, the connector and the component that it attaches to must be replaced at the same time or the repair will fail very quickly.
This connector like many that will be found was melted to the resistor and every wire had to be replaced. You can save yourself time and money by always being aware of changes in your vehicle and repairing them as soon as possible. If you need quality parts click here.
I recently completed a video on this repair as well. Please click here to view.
I am adding testing instructions due to popular demand. Testing is as follows. Disconnect the 7 wire harness connector and inspect. If there is any sign of heat damage replace both parts per above instructions. If there is no sign of heat damage then check the following. With the 7 wire harness disconnected check for power on the red wire. It should have 12 volts at all times and it gets it’s power from the 40 amp blower fuse in the under hood fuse box. Next with the key on check for 12 volt power to each of the following wires as you move the blower speed switch from low to high. Yellow / low, tan / med 1, lt blue / med 2, purple / med 3 and orange / high. Remember, this test is done with the key on and the seven wire harness disconnected. Other than the red wire having power at all times, only one wire at a time will have power on it, during a proper test. If there is no power to any of these wires during the test , check the fuse in the driver’s interior fuse box. If only some of these signals are missing, you will need to inspect the blower speed switch and related wiring. Also you should do a drag test on the terminals to check the spring tension. Please click here for more instructions
- Terminal “A” Tan = Speed 2, power through blower switch from HVAC fuse
- Terminal “B” Yellow = Speed 1, power through blower switch from HVAC fuse
- Terminal “C” Purple = Speed 4, power through blower switch from HVAC fuse
- Terminal “D” Lt Blue = Speed 3, power through blower switch from HVAC fuse
- Terminal “E” Black = Blower system, ground at all times
- Terminal “F” Orange = Speed 5, power through blower switch from HVAC fuse
- Terminal “G” Red = Speed 5, Constant power from BLWR fuse under hood
If for some reason the blower does not work at all and there is no power on any of the wires except the red , you may want to see the recent information I published about a new problem that has occurred. Please click here to see that article.
If all of the tests above are okay and you want to go a step further, place a test light or voltmeter in the wires going to the blower motor. If the light comes on or you have a 12 volt reading, the resistor and wiring are okay and the blower motor is faulty. This can also sometimes be confirmed by bumping the blower motor with the switches on. If the motor starts after bumping the motor is faulty. One can also remove the blower motor and apply 12 volts (power and ground) directly to the motor. Be careful though the motor will tend to jump and roll all over the place. Hold it firmly and be sure you are clear of the impeller as it could hurt you pretty easily.
One other note. If you have an amperage gauge, test the blower amperage draw while it is mounted in the blower case. Turn on surge amperage could go up to about 28 amps. Amperage draw at high blower should be in the 18 to 24 amp range. The lower the better. Restricted cabin air filters (if present) and dirty evaporator cores will cause a blower motor to draw more current while reducing air flow volume. These two conditions combined will significantly reduce the life of any blower resistor.
More additions to make parts identification hopefully easier. The following picture is of a floor mounted center console. In ordering, this is one of the most important features that we need to know about your truck. Please be sure to leave this information along with year, make, model, engine size, type of cab (regular, extended or four door) and confirmation that you have manual a/c. Leave this info in the customer comments box at check out when ordering. You may also email us anytime or call us 8:00 am to 6:00pm EST
The following picture is of an original two piece blower resistor that has been updated to a new design which is a single piece unit. If your truck has the two piece resistor, both pieces must be removed before replacing with the new single piece resistor.
If you have any questions related to this post please email me at info@the-electric-connection.com I just finished a video on this as well. Please click here to view.
Sparky, great information here, and it is very appreciated. My problem is similar. I have a 2002 silverado 1500 and today everything worked fine, then a couple of hours later my blower on high (5) won’t work, everything else does. I checked and there don’t seem to be any blown fuses. but it also doesn’t sound like the resistor issue. any ideas? your help would be greatly appreciated.
The Swede
Locate the junction block behind the panel on the end of the dash on the passenger side. Disconnect and reconnect the harnesses several times. Check to make sure no corrosion is present. Perform a system recalibration and see if the problem goes away. If it does great. If it does not get prepared to change the temperature door actuators.
Thanks Sparky, I’m going in. Bill
Hi Sparky, I have a 2004 Avalanche, last year middle of summer in route from Fl to Ct the passenger side Vents were blowing hot air, Driver side fine. Now it does it occasionally on either side. Things return to normal if I shut down the engine and restart (so far). Any easy fixes?
Check to see if there is constant power on the original red wire, terminal “G”. If it is not present, check the condition of the BLWR fuse in the underhood fuse box. If it is blown, replace it and your problem should be fixed. If it is good, there is likely a burnt terminal on the underside of the fuse box.
I remove the elbow and then use a shop (wet) vacuum to clear any debris from the hard plastic tube. Of course make sure the elbow is clear as well. Be sure to note the orientation of the elbow so that you will install it at the same angle. Also make sure it is not split and has a tight fit on the tube. If not you may wind up with condensation water leaking back into the passenger compartment.