Rear lighting issue/wiring diagram - 1995 Amtran Genesis

[Stan350]

Does anyone have any info, or a wiring diagram for the rear lights? We're having issues with the tail lights and we need to get them functioning so we can get our bus from freezing MN to somewhere south where we can finish it and then rewire if needed.

All front lights function as usual (head lights, turn signals, etc.)

Rear turn signals function as usual.

Driver's side red lights - always on high as if the brakes are being pressed, even when the bus isn't running but key is 'on' or 'aux power' position. Brakes do not need to be pressed for these light to think the brakes are on.

Both passenger red lamps functions as brake lights when brakes are pressed but do not light as running/tail light.

We've checked grounds that we could find and traced wires etc. we could find but not sure what we could be missing.

We don't necessarily need the running/tail lights to function, we can drive during daylight hours only if needed. We just need the brakes lights to function so we can legally drive it on the highway.

Any advice you could give us is greatly appreciated. Thanks in advance for your help.

 

[BlackJohn]

Brake lights being on such as yours are would appear to me to be a brake switch issue firstly. At the top of the brake pedal arm the switch can be adjusted to adjust the play in it. Sounds like yours is making all the time so you would allow more gap so it only activates when the brake pedal is pushed.
Air brake setup might be different, you didn't say which you have.
Tail lights out. Could be just dirty sockets. Replace if old but check for power first from a fused feed. Might even be a problem with the switch that turns them on if not in the headlight switch.
Good luck and let us know what you find.



John

 

[Stan350]

Thanks BlackJohn, and Happy Thanksgiving!

We have hydraulic brakes - so we have that kind of brake switch...but could a bad brake switch have lights working correctly on one side and not the other? Driver's side are bright all the time, passenger light up only when the brake is depressed - so they work correctly.

 

[BlackJohn]

Check everything you can see on the driver side. Wires good? Any splices bad etc.
Good ground connection of the whole socket and metal body of the same to ground.
That is likely the difference in how the sides are working different. The left has poor ground.


Is the bulb on the left the same type and number as the right?
Cleanliness of mating surface of the socket and bulb is often overlooked and gets one where you are, not that you have done anything. Something to clean while you open it up to check things.
Socket too body mounting holes often rust away so best check that. Sometimes the screws loosen after the years so maybe just tighten it all up first.


John

 

[Stan350]

followed wires...

followed the wires again - this drawing shows JUST the tail light wires and where they go. There is a second wire coming from the driver's tail light that goes to trailer wiring harness and another that has a plug, in line, that wasn't attached to anything.

 

[BlackJohn]

Disconnect the wiring from the solenoid to the whole socket on the right in the diagram. This will eliminate one feed.


The left side appears to have another feed.

I'm thinking from the brake switch only now, which to me seems normal.



Can't explain why that wire is there from a 12v solenoid and connected as such. Certainly constitutes a second feed.



Check operation after this change you just made.


Do you intend to keep the trailer wire and the other nothing socket?

If not, cut and tape them off there for now but cut them longish so you have something to work with later if need be.


John

 

[Stan350]

Wires are good, connections are good.

Entire bus was stripped of siding and it's all new galvanized steel (not painted yet, definitely not rusted yet). Passenger light was good but driver side was rusted so cleaned up and painted with rustoleum this summer. Probably need to get rid of some of the paint to make sure it's grounded? Will check bulbs for type and number. Thanks for more places to look. Appreciate it.

 

[Brad_SwiftFur]

Check and make sure the bulb isn't in backwards, the "brake" filament is not on the "running" lights side. Fairly common thing with the old 1157 type bulbs.

 

[Stan350]

detached from solenoid...

Cleaned driver's side bulb, fixture, wires, grounds, made sure in correctly etc. - still on as brakes all the time.

So...removed the wiring to the solenoid and the driver's side now does nothing. Passenger still lights when brake depressed - good.

Tried grounding the wire I removed from the solenoid - still nothing at all on driver's side. Passenger side still good.

 

[BlackJohn]

Do a voltage test on the right and then feed the left with that source.
Do a voltage test on the driver side, anything?

Why are you grounding the solenoid wiring? isn't it still "hot" but disconnected from the passenger side? Are you sure it is from the solenoid?
How did you prove that?


You will have to determine which wire go from side to side and to the proper socket.



John

 

[Jolly Roger bus 223]

The light body is the ground.
You painted them and probably put the same screws back in the same holes?? Clean the paint off of the backs of existing light bodies and the bus boddy a 1/2" up or down. Turn the light a 1/2" and put new self tapping screws in it.
The old screw holes and light base are probably gone.
They require the base of light to ground or if heavy paint the screws in the light to the body are the ground GROTE lighting makes and has almost every lighting product we need with better gasket ting but it still requires a clean grounding surface? Whether it is the light base or a good clean screw?

 

[BlackJohn]

The light body is the ground.
You painted them and probably put the same screws back in the same holes?? Clean the paint off of the backs of existing light bodies and the bus boddy a 1/2" up or down. Turn the light a 1/2" and put new self tapping screws in it.
The old screw holes and light base are probably gone.
They require the base of light to ground or if heavy paint the screws in the light to the body are the ground GROTE lighting makes and has almost every lighting product we need with better gasket ting but it still requires a clean grounding surface? Whether it is the light base or a good clean screw?

Thanks JR. I had completely forgot about the new paint. Could be the reason for sure as well as needing remounting in new holes.
OP, any pics of what you got there?


John

 

[Jolly Roger bus 223]

I made the mistake when my reverse lights had problems cause the new GROTE lights are all plastic. I could wiggle the light and make it work but the true answer was the screw hole was rusted. So I twisted them a 1/4" and put new screws in.

 

[Stan350]

Got it!

Finally decided to just skip trying to do it the way it was - or was supposed to be and just connect the wire that was to the solenoid to anything and everything one by one until they worked. Found a winner when we connected it to the wire that went from the pass. light to the brake switch. Wa la, functioning brake lights. Now we can get south before we run out of firewood and freeze. Thanks everyone for your suggestions and for letting us know that wire didn't need to go to the solenoid.

 

[BlackJohn]

Does anyone understand what he just did? I sure don't follow. How can anyone learn from this explanation?
Can you explain this better than you have?



John

 

[Stan350]

the wire that went to the solenoid that you told me didn't need to go to the solenoid - I disconnected it from the solenoid and then just tried connecting it to other wires until it worked. Not electrical, just desperate. It finally worked when I put it inside the same wire nut that connected the passenger light to the brake switch.

 

[BlackJohn]

This still makes no sense Stan. You disconnected the solenoid wire, so that means it is open ended, going no place. Is one end still connected on the solenoid?


This has been frustrating to say the least but somehow you have working brake lights. A very hard diagnosis from here with no pics, no drawings, a sketchy sketch and newly painted body metal. Did you pull the lights off the vehicle or just mask them for painting?


In my mind I had a picture of what a simple brake light circuit should be and tried to convey that best I could. Your eyes did the bulb and socket inspections which turned out ok. No corrosion or questionable wiring as far as corrosion goes.


So, maybe my thinking is all wrong.
There is more than one way to wire brake lights it seems.



1) My way of thinking was that the hot wire for the brake lights came thru a fuse to the brake switch, then to the 2 brake lights at the rear and grounded through the body connection. That is as simple as it gets and how my thinking went originally. It should work this way everything being good in the circuit.

Being stubborn I went with that idea so that is why I did not understand the hot wire being there from the solenoid.



so



After no understanding why it would work on the passenger side and not the driver side I had to reconsider after reading that you got them working.
Perhaps the feed does need to come from the solenoid, thru a fuse or breaker and back to the brake sockets and then grounded. The grounding in fact must happen when the brake switch is pushed, thereby lighting both sides at the back. Without pics I could not see for myself the sockets and how many wires were on them. They would have to be wired in parallel and so that would be one wire on each. If there is/was a second wire that might be an independent ground wire for each. With the passenger side working only, this now makes sense to me. It was grounded through the brake switch where the driver side wasn't.

Once you grounded the driver side properly using the brake switch wire, it finally lit up.


We never talked about the brake booster electric pump but it gets grounded also when the brake pedal is pushed. This happens if the bus is running or not. Call it a safety feature to ensure the brakes always apply in any situation, if hydraulicly operated.


So for safety sake, they ground these lights through the brake switch as the body cannot always be depended on for a good ground.
A good idea too but not easily recognisable without seeing the electrical schematic.


Enjoy your trip to warmer climes!


John