W250Redneck

ok so im juss about ready to drive my truck now, but my winshild wipers are acting up. when ever i turn on my lights or hit anything but the off button on the hvac control, my wipers turn on. when i turn the wiper switch on to off, they will turn off for 10 seconds or so. they work fine other than that.

ive looked through various electrical threads and read that there is a ground on the wiper mount, and that i should look at the headlight switch for any loose connections.

any help would be great, thanks guys.

Kyle

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92 W250, auto, ex-cab, 128K, primer grey

wannadiesel

Check the main body ground on the core support by the battery.

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Faith
'93 D350 - DPS 6x16's, HTT Stage IV/14wg, PowerStroke IC, Snow water/meth, Walbro 392, Con-FE, pump tampering by owner.
386 HP/774 TQ on #2 only, 408 HP/844 TQ w/ water/meth - needs more air!
Dead KDP's = 72
wannadiesel@dieseltruckresource.com

TIMMY22

You did'nt by chance change the stop light switch, did you?

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96 2500 4x4 Auto, No payments, No silencer ring, KDP barrier installed, Thuren Bar, 4" Strait Piped, Star wheel tweaked, Air Ride Rear, ~177K

92 D250 LE 4x2 5 speed, No payments, No Muffler, No rust, Locktite on Killer Bolts plus KDP, EGT and Boost Gauges on A-Pillar, Fuel screw 1 turn, Smoke screw 2 turns, Timing bump, 366 Spring. 3.54's, ~155K

91 W250 Gas to Diesel Conversion, Auto 727, 3.07's non I/C, Custom Turbo back 4 in. exhaust, KDP killed, Body off Chassis restoration ~216K

W250Redneck

I may have, because one came with the cab i got so its possible. but what would that have to do with the wipers? do the wires connect somewhere along the line?

TIMMY22

actually, yes....

If you put a cruise control equipped stoplight switch in a non-cruise wiring harness, the wipers will have a mind of their own. Ask me how I know. Unplug the stoplight switch and see if the problem goes away. Has to do with the white wire with tan stripe.

I figured this out when I compared wiring diagrams. The no cruise stoplight switch is 4 wires and the cruise is 6 conductors. If you study the schematic, you can see where you will get back-feed.

TIMMY22

I just looked at the schematic again. If the problem stops when you unplug the stoplight switch, you can...

1. Swap in a 4 conductor (non cruise) switch. or...

2. Modify your(w/cruise) switch by taking a pick and pushing the two conductors not needed out of the plug. It's the Dark blue w/yellow stripe and the yellow w/red stripe that you want out of there. Usually there is a barbed tab on one side of the plug you just bend back with the pick then give it a push and it should pop out.

I would not just cut them because you will have a hot wire dangling under your dash.

W250Redneck

but i have cruise control. i dont know if it works or not. could it possibly have the same reaction if i put a non cruise switch on a cruise equipped wiring harness?

TIMMY22

Did you try unplugging the stop light switch?

TIMMY22

Not sure...

I swapped a '90 diesel dash wiring and engine bay harness into a '91 gasser truck with cruise. The '90 did not have cruise. So, it was like I was trying to put a cruise SL switch into a non-cruise harness. Ended up having wipers that would come on with the directionals and hazards etc. I stumbled across the SL switch as the culprit with the back-feed coming in from that white/tan wire.

The other fun was splicing the '91 steering column into the '90 harness. The '90 column was all hacked up and shot so I couldn't just swap the column. The '90 used the key switch with rods controlling the ignition switch down low and the plugs were totally different. It ended up being a 32 wire splice spaghetti

Other than the stoplight switch problem at first, it all works! The wait to start light works, everything but the cruise is working.

W250Redneck

well unfounantly my truck is at my dads house and i havent been abel to get up there. so i havent had a chance to try.