4104 Headlights

4104SoFl · October 10, 2015, 10:09:56 AM

Trying to get my headlights to work on the bus.
I have clearance light that work.
Having trouble with the headlights
Need to re wire them. One wire should be ground, one wire low beam and one wire high beam.
I have all three wires to the headlight hot.
Even thoe I only have one wire hooked up.
Help please.

zubzub · October 10, 2015, 12:06:47 PM

Probably a failed hi/lo switch, they do not last. If it is no that, run new wires, on mine the old wire's casing had frayed and they were shorting to each other.
Get used to using your multi meter, repairing stuff, you have an old bus.

Oonrahnjay · October 12, 2015, 04:54:01 AM

I don't have any experience with a bus of this type so it may not apply, but some older buses had a wiring system that used 12V headlights in a 24V system. There are two problems with this ... when they don't work, it's sometimes hard to find problems because those systems don't follow "usual" rules -- you have to know where to look for 24V and where to look for 12V; the other problem is that by now they have often been "repaired" by someone who doesn't really know what he's doing and you get all kind of weirdness.
As Zub said, you have to take your meter and go back to basics and trace. You do have a wiring diagram, don't you?

4104SoFl · October 12, 2015, 05:42:35 AM

All I have is the maintenance manual.
Yes, there has been some work done by others
Much of this wiring look original, but some has been changed.
I would love to get the wiring diagram that the book calls for.
MD-75571 is what the manual calls it.

rgrauto · October 12, 2015, 06:31:15 AM

Unplug the headlight and test the elct, connection with a test the light. Ground the test light on the body,grill ect. and turn on headlight switch and determine which wire is low beam and which is high beam and the third should be ground. usually it is the ground you are missing. Be sure to unplug both headlights for test to work.

4104SoFl · October 12, 2015, 06:38:02 AM

10-4
Later this afternoon when I get done working.

zubzub · October 12, 2015, 12:48:57 PM

Someone here or at the yahoo gmc buz site? Has a PDF of the shop manual that includes a wiring diagram. It is free ask around.... Your manual had a diagram at the back when new.

chessie4905 · October 12, 2015, 05:59:23 PM

Headlights should be separate from marker lights and on small metal circuit breakers. Check to see if breaker is bad.

TedCalvert · October 12, 2015, 09:16:15 PM

The 4104 was all 12 volt, no 24 volt involved. They were originally positive-ground, may be converted to negative-ground. That's not an issue, don't let it confuse things.

4104SoFl · October 13, 2015, 01:33:37 AM

Thank you PENNUJA
Got it.

4104SoFl · October 13, 2015, 01:52:56 AM

OK, clearance lights when you turn them on, come on then you here a clicking sound coming from the panel on the left side of the driver.
Some sort of relay. Clicks again and they come back on. Looked at the wiring and it is old, and crack all over. Wiring in the panels on the dash and too the left
look good. Only a couple of newer looking wires. One run too the headlights. So i know now that the wiring for the clearance light has to be replaced. Now I need to find out how (where) the wires run. Do I have to pull all the cabinets down or what?

uncle ned · October 13, 2015, 08:31:53 AM

On HUGGY you have 2 different toggle switches for the clearance lights and the head lights.

By the way a 04 is all 12 volt no fancy wireing for the head lights needed.

Hot wire to the dimmer switch and a wire to the dim and a wire to the bright side.

uncle ned

4104SoFl · October 13, 2015, 08:47:35 AM

Thanks for the 12 volt.
Working on it this afternoon

zubzub · October 15, 2015, 04:26:43 PM

Quote from: 4104SoFl on October 13, 2015, 01:52:56 AM
OK, clearance lights when you turn them on, come on then you here a clicking sound coming from the panel on the left side of the driver.
Some sort of relay. Clicks again and they come back on. Looked at the wiring and it is old, and crack all over. Wiring in the panels on the dash and too the left
look good. Only a couple of newer looking wires. One run too the headlights. So i know now that the wiring for the clearance light has to be replaced. Now I need to find out how (where) the wires run. Do I have to pull all the cabinets down or what?

the click is the fuse tripping, they reset automatically, then trip again. Find the PDF of manual to wiring diagram. The panel by the drivers seat is the front Junction box...might as well open it, and leave it open til you work it out. I ended up just running fresh wires to all the clearance lights etc as most were shorting to ground. Fortunately other than lightning most of the 04's wiring is fairly straightforward.

4104SoFl · October 15, 2015, 05:13:24 PM

I believe this to be true.
Someone from the board was kind enough to send me the missing pages to the manual. I was missing the last 30 or so pages.
My question is how do I rewire. I pulled I cabinet down on the right rear. Still could not get to the wires.
So please tell me how I get to these wires?