Wiper pulse board smokes

[JCribb]

1989 c1500 w/delay wipers.

I got the ever so common 88-91 wiper issue. Looked it up, found the 92-up swaps right over. I tried this twice now, and nothing.

First one was from a 98 Tahoe at the junkyard, it didn’t do anything.

Second one was a brand new unit from rock auto. I ordered it for a 98 Silverado, plugged it in, circuit board starts smoking immediately after I turn the switch on.

Someone, or multiple someone’s guide me in the right direction please. There’s obviously an electrical issue I need to find.

If I plug in the old motor which works on high only, I have wipers, but if I plug in the updated motor I get nothing.

 

[DerekTheGreat]

How's the multifunction switch? The swap is indeed a direct swap though, I threw away my brick style wiper motor for the later one and it's been good ever since.

 

[JCribb]

I’m sure the actual wiper switch is beyond useful. I did find burnt/ melted wires and, a couple jethro rigged jumpers to what I don’t know. There just happened to be another 89 c1500 in the junkyard with a good dash harness and manual column. So I went and grabbed up both parts today.

 

[DerekTheGreat]

Good ole Jethro knows just enough to get the problem in someone else's driveway.

 

[someotherguy]

I think I've seen a few earty GMT400's with a module inline on the wiper harness that had to do with a variation of the intermittent wiper motor. This was long before I'd learned there were so many differences in the year models so I didn't pay it much attention, then I want to say I'd seen a similar module on a TBI-era squarebody truck. I wish I had more info but you may want to look closely and be sure you don't have a little module plugged inline on the harness that comes from the steering column for the wiper motor.

In other words while we generally consider the 1991-up intermittent wiper motor a direct swap into the 1988-1990 trucks *when equipped with intermittent wipers already* - that may not be a 100% correct statement as there could be the oddball truck out there. Also beware that in those early trucks especially the lower trim levels there are ones equipped without intermittent wipers and the switch in the column will be incompatible.

Richard

 

[JCribb]

I think I've seen a few earty GMT400's with a module inline on the wiper harness that had to do with a variation of the intermittent wiper motor. This was long before I'd learned there were so many differences in the year models so I didn't pay it much attention, then I want to say I'd seen a similar module on a TBI-era squarebody truck. I wish I had more info but you may want to look closely and be sure you don't have a little module plugged inline on the harness that comes from the steering column for the wiper motor.

In other words while we generally consider the 1991-up intermittent wiper motor a direct swap into the 1988-1990 trucks *when equipped with intermittent wipers already* - that may not be a 100% correct statement as there could be the oddball truck out there. Also beware that in those early trucks especially the lower trim levels there are ones equipped without intermittent wipers and the switch in the column will be incompatible.

Richard

I appreciate the heads up. I did go ahead and grab up the junkyard column and under dash wiring harness to swap into mine, both same year, both Scottsdale trim level. The only difference between the junk truck and mine was two cylinders, junker being a 350, mine a 4.3.

Both trucks were CD4 equipped, which is the RPO code for intermittent/ pulse wipers.

Eventually I will rebuild the column from my truck with all new parts, or it may become the parts column depending on how things go. Someone had previously been in it goofing around, because when I took it apart the snap ring was missing, and a few things were loose.