After finishing the headlights in Electrical 7: Headlights it was time to track down why the heater blower motor wasn’t working. The symptom was a blown fuse as soon as I pressed any of the heater buttons. No power means the motor doesn’t work.
After changing several fuses I confirmed that the problem was in the blower circuit. It looked like something was creating a dead short. This could be from the new wiring harness, or I could have pinched something when re-installing the heater plenum.
The speed control for the blower motor goes through a big resistor mounted on the firewall in the engine bay. I started the underhood troubleshooting by unplugging one of the wires from the resistor.
Umm, why does this wire say NEUTRAL SAFETY SWITCH???
Krud. In the new wiring harness both of the wires for the blower resistor plus the wire for the neutral safety switch are all brown and come out of the wiring harness at the same location and have the same connectors on the end.
This is why it is critical to READ THE FREAKING LABEL (RTFL) when you are connecting devices!
Yup, the wire connected to the neutral safety switch says HEATER BLOWER MOTOR.
Connect the wire labeled NEUTRAL SAFETY SWITCH to the neutral safety switch. Now plug the wire labeled blower motor into the blower resistor. Hmm, its a bit too short. OK, wire up an extension with a new plug and plug it it.
Now to check the blower motor: No blown fuse! And the heater blower runs at low, medium, and high speeds. There wasn’t any rejoicing this time – I was too annoyed with myself for making such a stupid mistake.
The last thing was to try to start the car and make sure the neutral safety switch still worked. The Imperial fired up immediately, so that part is still good.
All that work labeling all the wires and then I don’t pay enough attention when actually hooking everything up. At least the problem was obvious when I finally looked. Grumble.
On a side note: If you are going to be doing a lot of electrical work it is a good idea to buy fuses in bulk. The retail price of automotive fuses can be over $1.00 each. Or you can get them for less than a dime by ordering 50 or a hundred at a time – for example, 20 amp mini fuses for eight cents apiece. Since it is easy to go through several fuses when tracking down a problem (at least for me…) it is good to have a box full of fuses available.
The next job is to figure out why the alternator isn’t charging.
Next: high current upgrades in Electrical 9: Up Gauging.