Rear heater/AC, rear turn signals, rear brakes and rear flashers don't work

VINTSHAVE

MEMBER
1993 GMC TRUCK
5.8L
V8
2WD
AUTOMATIC
180,000 MILES

Hi,

1993 GMC G3500 Vandura based school bus

I just got this former school bus. Overall it's in great shape, but it has electrical issues - particularly concerning the school bus-framed electricals. I know that when a school bus is decommissioned, they remove a number of the school bus features and repaint it.

The electrical panels above the visor, in the school bus body. The other side of the squarish unit shows the image of a school bus with led indicators to show what lights are on. This never worked. The longer set of switches has only three active switches installed "Dome" (which works), "Master Warning" (does nothing) and "Recycle) (does nothing).
You can also see a panel which is exposed when I took a plate off near the top of the bus.

There are tons of wires up there with little clue as to which ones go where. There is no schematic I can find. The major things I MUST accomplish are:

-Get the rear brake lights working. No idea why they aren't
-Get the rear turn signals working. Front turn signals work fine
-Get the hazard lights working. When I pull the knob, I get one flash and then they just go out.
-Get the electricity running to the rear heater/a/c unit

The company that made the bus body is out of business, so I'm SOL on the schematics. I need to get the first three things working just to get it inspected.

Thanks in advance for your help.

John

2 Replies

VINTSHAVE

MEMBER
62 POSTS

Figured out the rear brake lights. It's a 2 filliment bulb with one bad filliment. Screws hold the lens housing to the bus. Something I can't figure out holds the lens to the housing. I've tried every Allen wrench I have and no dice. So, problem there.

If the Amber lens to the left of the 7" red lens is the turn signal, I can see why it's not working on the drivers side. There is an internal panel in the bus behind the light and the wire was snipped at the crimp. Why? Who knows. But I have no ideal where the wire that connected to it is. The only other thing I see is a yellow wire that is also cut at its crimp. But the wire going into the Amber housing is black.

The other side is also not working, but there is no access panel. To get behind the light to look Id have to drill out about 15 rivets. Are school busses really designed so that you must cut rivets to access the back of a light fixture?

If I knew what color the turn signal wire is and how to test it, I'd have a much better idea of how to get it fixed.