1993 GMC G3500 Vandura based school Bus - Serious electrical problems

VINTSHAVE

MEMBER
1993 GMC
5.7L
V8
2WD
AUTOMATIC
179,000 MILES

I am about at my wits end. I had a busted hazard switch. The hazard switch is in the steering column, so I pulled the steering wheel and the lock plate and carefully replaced the hazard switch. I put the whole works back together again. I checked for loose wires or un-connected connectors and there seem to be none. I am now having the following problems:

-I have NO brake lights. Tail lights are fine and so are backup lights.
-I have no PRNDL light
-The left turn signal does not "reset" when I turn the wheel. The right one does.
-There is something being randomly actuated (a plunger attached to a cable) that sits by the brake pedal. It only happens when the key is in the ignition. I checked to see if the brake lights go on when this happens, but they don't.

I have been working on this truck for a week. I MUST get it inspected and I can't afford to have someone do this for me. I obviously can't drive it with no brake lights. The wiring does not match the wiring diagram in the chiltons book in the slightest. I am at the point of tears.

Please help!

2 Replies

HOMER1967

MECHANIC
875 POSTS

It sounds like you didn't get the multifunction switch lined up correctly, but diagnosing this type of issue without being able to see it is next to impossible. The fastest, easiest, safest and least expensive thing for you to do at this point would be to replace the steering column.A couple bolts and a couple plugs and your done.

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Monday, November 17th, 2014 AT 4:59 PM

VINTSHAVE

MEMBER
62 POSTS

I was not all that hot on replacing an entire steering column to solve a couple of electrical issues, but your focus on the multi-function connector gave me an idea. I compared the original GMC connector with the crappy Autozone OEM one. There were a couple of slight difference. To make a long story short, once I made a couple of simple modifications, the PRNDL light came on when it should and the brake lights worked too. One oddity - the brake lights USED to be the two red lights on the back of the truck (which are also running lights when the headlights are on). Now the red lights work as running lights only. It's now the AMBER lights that function as both brake lights and rear turn signals. If I am braking and have a turn signal activated, the brake light is not activated on the turning side, but it goes on on the other side of the truck, which I believe is how it's supposed to work. Not exactly sure how the brake light function jumped from the red to the amber, but if it's legal, I'm good with it. :-)

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Monday, November 17th, 2014 AT 6:22 PM