My son has a 98 Aurora (Dad’s old Olds) where the fan / blower no longer works. He doesn’t like to use the fan and now he has no option. My question is this, how do I determine if it is the blower motor or the electronic control module? I’ve read that both contribute to this problem equally. I have the service manuals (thank you eBay) but need some advice on finding which is the culprit.
Usually, (based on reading and personal experience) the resistor block is the one that dies first.
You can test the continuity from the fuse panel (I would ensure the required fuse DOES work) to the fan speed switch, from the switch to the motor or from the power source directly to the motor (via a jumper wire).
The service manual DOESN’T explain/show how to test the circuit? Is that the SHOP manual or a Haynes/Chilton?
If you have the real factory service manual, just see the appropriate trouble shooting chart. If not, the short way is to first check the fuse under the back seat, check for voltage at the blower motor connector when you are commanding blower operation, and finally you can apply 12 volts directly to the blower motor connector to see if it works or not. If the blower works with 12 volts, its switch or blower module. If it doesn’t work, its the blower itself.
As mentioned, check the fuse for the blower motor circuit.
If that checks out okay, then you have two choices in determining if it’s the blower motor. Unplug the blower motor electrical connection, and either test the wiring harness to the blower motor for voltage while operating the blower control, or apply DC voltage to the blower motor terminals.
Tester
The blower relay is another possible trouble area. If voltage isn’t getting to the electronic speed controller then that is a likely suspect. I assume you already checked the fuses in the dash and under the hood to make sure they are ok. If not, then you need to do that first.