2003 GMC Sonoma Heater and Wiper issue

[C0RR0SIVE]

First time posting here, sorry for not properly introducing my self.

I am the family mechanic, and have a 2003 GMC Sonoma with the little 2.2L engine sitting here. The truck has been an amazing truck since we purchased it 100,000+ miles ago used, nothing has ever gone wrong with it till very recently.

Last summer my sister, the one that owns the truck complained that her wiper blades would stop working, but, I never could figure out what was wrong, because they ALWAYS worked. I did my research and heard about the circuit board on the motor causing issues. But, it doesn't explain the next issue.

This past month, while I was driving home in a downpour of rain (we had a drought since the last complaint, never bothered to look), the wipers died, but since I was driving with it being cold out, I noticed something else also stopped working at the exact same time. The blower motor for the HVAC fan stopped. Nothing related to HVAC, or the wipers operated, but the radio operated, as did the dash gauges and everything else.

I decided to look at my books to see if I could find a wiring diagram and see what these two systems have involved that could cause both to fail at the same time, only to discover neither system is listed in my books.

I have checked all fuses, and connections that are easily accessible for both the fan and the wipers, all are in good condition.

Does anyone have any good solid advice, or steps I should proceed in? This is one of the most bizarre issues I have ever encountered with a GM, and sadly, this time of year, heat and wipers are kind of essential...

 

[fishin_wi]

i had almost the same problem b4 with the wipers, exept they would sometimes would not shut off. Yes the circuit board is the problem, I guess the case that it is in isnt water tight, and corrodes terminals/connections. As far as the heater goes....does it have a resistor pack? My 2000 model did, and they do burn out almost like a light bulb filament. It should be fairly accesible under the hood too, near the firewall on passenger side. I'd start there, and you could test for voltage at the connctor while you have it unplugged. Good luck and let us know what you find!

 

[C0RR0SIVE]

Well, the key issue is, is that both systems stop working, and start working at the exact same time, I doubt that both the blower motor resistor and the wiper pulse board would act up at the same time all together on numerous occasions. This is why I came here, to see if anyone has had this exact problem (Both the wipers and fan stop working at the same time, then both suddenly start working at the same time a few days later), or a few wiring diagrams that I seem to be missing related to each systems circuit. About the only thing I could think is they have a common ground, or common 12v, but with out a wiring diagram... Le' Sigh. Guess my next weekend off I will open things up and take a looky.

 

[drwet]

You need a wiring diagram. Without one you're just guessing. But if we're guessing, I suspect you are on the right track looking for a ground problem.