Tearing my hair out problem with 1997 Sierra SLE k1500

[someotherguy]

Well, took cover off wiper motor. Thought it was going to break. Didn't realize the board was glued to the cover. Looks like new. The PCB looks pristine. No cracked solder points or discolouration at all. Even carefully pried up a corner of the board to peek at back and it looks new as well. The one contact point was wore more than the other but there was still tension on both. Cleaned the ground as well. We'll see if it stops or fails to park.

On another note while driving home late last night with high beams on they quit after 30 minutes. Sat for 10 minutes with switch off and they worked again but only for about 10 minutes. Waited again and they came on so drove the rest on low beam. Years ago I replaced high beam with 65 watt bright whites and it occurred to me it's been years since I had driven any distance on high beams. Checked that ground but it was less than 3 ohms. Cleaned it anyway. We'll see.

The covers aren't glued to the board. Something weird going on there. I wonder if that's a reman wiper motor and the builder put some kind of goop in there?

At any rate, you can have cracked solder joints so small you need a magnifying glass to see them. You can trust me on that, I have ridiculous amounts of soldering experience in particular fixing bad joints on old equipment (I fix up classic pinball machines as a hobby.) BUT - the other ground issues you've found are likely contributors.

Richard

 

[Chevy529]

someotherguy;

I was afraid someone was going to point that out .

It was covered in some kind of red spray on "protectant", well, half the board was. Mostly where the capacitors(?) sat. There was writing on the board even calling it some kind of coated board though I cant remember the exact name.

DTRL dont work
Cargo lamp bulbs burnt out
and now ... the door buzzer will come on with key out and stay on ... or not.

Somebody mentioned something called the "school bus effect" where the DTRL can backfeed power and cause all sorts or weird things to happen.
ANyone ever heard of that?

 

[Chevy529]

Well, had time get into it further. Turns out the DTR lights were back feeding power to the multi function switch. Which turned out to be the problem. The harness at the connector was crispied and causing random problems. New multi function switch is $670.00 plus 10% tax at dealer here in Canada. My nephew brought me one from USA for $60 all in. It may not b same quality but it works and I can change it every year for a decade and still b money ahead. Going to do the upgrade on the lights now for the 4 high setup. Using the switch as a control only.
This was a royal PITA but thanks to your help it's almost fixed. Very much appreciated!

 

[Chevy529]

Forgot to mention. The backfeed cooked the diode so I bypassed it when I added relays. I was looking for a tiny diode but couldn't find it even with wiring diagrams. This thing is MASSIVE. 2" x2" x3" with cooling fins. I looked at it 29 times thinking " it CANT be that". It was. Oops