F/u: relation between the blower and the brake warning light

A few weeks ago, I posted a note here about my Chevy Malibu (1999): When it starts up, sometimes the blower does not work, and the brake warning light will be on. After about 10 minutes drive, the blower starts working again, and the warning light will be off, and everything seems fine. I got some response from this forum suggesting it is a wiring problem as the blower and the brake wire must share something at a certain point, and I need to use the wiring diagram to track it down. One of my friends thinks this is a sign of the ignition switch going bad: when the blower does not work, the ignition switch isn’t powering up all the circuits. That’s proably why the brake light is coming on when it’s not powering up that circuit also. After a few minutes, the contacts in the switch gets hot and stars to work. He thinks replacing the switch will fix the problem. What do you think about his diagnosis? Is there any way to check if there is anything wrong with the switch?

You really need to use the schematic, this is the way electrical problems are figured out.

If you do your own work, ignition switches used to be about $20 and were easy to change. The instructions just make it seem difficult.

My other story probably won’t help your situation. It was a right tail light that wouldn’t work. After tearing out three sets of aftermarket stereo wiring I managed to see two wires stuck together that looked burnt. I separated them and taped them up and the problem was gone.

Another story might help. Bad grounds make strange things happen. Look at your dashboard grounds; they might need tightening. Your engine to body ground could also be doing it. It can really stop things like heater motors (rarely) and windshield wipers (frequently when raining). On 70’s Toyotas it would cause the engine to stall if the AC was turned on. Scrape the body end clean and reconnect.

Your friend may very well be correct. If the switch is getting hot then that is a pretty good sign that the switch contacts inside it are bad and replacing the switch very well could solve the trouble you are having. Using a voltmeter you certainly can check the voltage on the leads after the switch to see if there is a voltage drop though the switch when it is turned on. If there is a problem the voltage on the switched side will be less than the input side of the switch.

Thank you so much for the information. I’ll check the tail light wiring as the bulb burns very often. Incidentally, where is the dash grounds located as i want to check it as well. Thanks again. Lee