This 1997 GMC Savana van has a problem with the blower speed dropping without the switch being moved. The resistor as you can see in the picture below is quite easy to get to. It is under the hood on the passenger side of the vehicle.
If you would click on the picture below to enlarge it, you will see a slight discoloration of the third terminal from the right in the picture below. That terminal is in the “C” cavity of the harness connector and the wire color is black. This is the main ground for both the blower motor and the high blower relay that is within the blower resistor assembly. You should also be able to see that terminal “A”, red wire at the far right is also slightly open. Both of these terminals are in the process of failing. When a condition like this is encountered, the blower resistor and the harness connector should be replaced at the same time. The driver should also be informed to not use the high blower speed for more than about thirty minutes at a time, with at least a five to ten minute rest before going back to the high blower position. The evaporator core needs to be checked for debris that may be restricting air flow. The van needs to be checked to make sure that all window and door seals are good and in place.
Removing the blower resistor from this point is pretty simple. Push in the locking tab at the blower motor harness connector. Then pull the wiring from the blower motor.
The wires are secured behind a plastic hook on the heater-a/c case.
A closer look at the hook. It seems kind of like misplaced priorities by the design team. Their time could have been better spent designing a heavier connector or better body seals. I say body seals because if the van was sealed better the driver might decide to turn the blower speed down and not just leave it on high all of the time.
Enough of the belly aching. There are two 5.5 mm headed screws that hold the resistor in place.
The new resistor is slightly larger than the original and the hole has to be enlarged as a result. There should be a template in the box with the new resistor. The customer was not ready to do this repair so I cannot show how to cut the box. It can be doe with a good utility knife or a hacksaw blade. There are power tools that will work as well. A couple of things to keep in mind while doing this modification.
Do not damage anything inside the case. Can we say Evaporator Core?
If you use a hacksaw blade or power tool, also us a shop vacuum while cutting to remove the cuttings before they fall into the case. Make sure the interior is clean before installing the new resistor. Dirt and leaf build up can cause the blower motor to draw too many amps while it is working and this can cause early failure of the new part.
Make sure the enlarged opening will allow the resistor to be installed properly but also make sure that you do not cut beyond the sealing edge of the new resistor, or you will have an air leak and possible water intrusion.
The “M Van ” template is for Astro and Safari Vans. The “GMT560/610” template is for Express and Savana vans.