Light Wiring Problem

All right guys and gals...have a wiring problem. I have finished my resto on a 75 CJ5. Original wiring harness. Dedicated grounds from back to front all going to a buss bar. Everything was working as it should until the brake lights went out. Check the fuse and it was blown. Replaced and now I have brake lights. However, when I hit the pedal, the park lights come on with the light switch off. With the light switch on, the park lights turn off when I hit the brakes. Additionally, the hazard lights will only work if I use the turn signal at the same time. I thought maybe one of the signal/hazard flashers was out so I swapped them with the same result. Any help would be appreciated. I'm at my wits end.

 

Got some wires swapped somewhere or a bad ground .. You need to find a wiring diagram and chase it out.

I'd start here: Jeep Wiring Diagrams - 1974 and 1975 CJ

 

I would normally agree with you however everything was working fine until the fuse blew. I have a factory manual and can’t seem to find any miss placed wires. Also, I have dedicated grounds going from the rear lights to the bus bar and a separate ground for the front. I’m wondering if there is a problem with the spartan turn signal switch?

 

From your description, you have a bad ground. The brake lights are grounding thorough the parking lights. You confirmed this when you said the park lights come on when brake lights activate and go out when you turn on park lights. Verify that the lamp assembly ground(s) are good.

 

this is a glass tub? it is a bad ground somewhere, you need to ground everything,all lights, the dash, the column, the blower motor,if its electrical it needs a dedicated ground,and they must all be clean and tight,one loose one and you are chasing the gremlin...

 

Quoting your post 1308301:
"So I am in the process of rebuilding my Sparton turn signal switch. I have a NOS 4 wire one which I am cannibalizing. The NOS one has the light for the housing whereas my original one does not. Is there a way to retro fit the light into mine. I used the housing from the NOS one which has the green indicator glass (ie plastic). Just wondering. Thought it would be cool to have. Thanks unquote

Is this why you question the Sparton switch? Note that the four-way flasher uses a separate fuse than does the regular turn flasher. Don't know the fuse rating for these two circuits. If something went bad in the T-sig switch and connected the front lights with the rear during a stop, then it's possible to overload the T-sig/Stop fuse and blow it. Just a suggestion here.

 

To answer some questions...It is not a glass tub. I did not end up converting my turn signal switch as I never got a response on how to change it. After some interrogation, I might have found the problem. The wiring loom to the rear lights is pinched between to roll bar and tub. I wonder if it has sliced through the wires. Going to check in a bit. Ill let you guys know what I find. I hope this is the problem. Thanks for the suggestions thus far.

 

Ok here's an update. I freed the pinched wires and saw no chaffing. I then disconnected the hazard switch. When I hit the brakes, I get brake lights without activating the park lights, When I pull the light switch, I get headlights and front park lights but no rear lights. I have checked all my grounds and see no issues. Do you think the hazard switch could be the culprit?

 

Do you have the TSM? The '74 and '76 diagrams arw available here Jeep® Parts Manuals online as part of the manuals. A '75 is more like a '76 except for the steering column. The '74 has no fuse panel, but the steering column is the same as the '75. The steering column wiring is an important character in the current story.

I believe the 4-way switch connects to the turn indicators through the steering column, so it takes over both sides of the indicators. I can't right now, but one could trace through the wiring diagram and figure out the path for the 4-way flashers. Once you know how it should work, you can remove the switch and see if it is functioning as you expect. The switch has 5 connections - likely flasher signal in and a connection to each side, front and back.

Sorry if I'm stating the obvious, but I think you will continue to chase your tail if you keep making guesses. With electrical, you need to go step by step and use your test gear (test light, multimeter, or whatever you prefer). I would get a sheet of paper and the factory diagram and trace out the complete circuit. Then I would start at the battery end and trace it through to see where it stops behaving as I'd expect.

 

chosen 1608 your post #3 refers to the sparton turn signal switch? The 75 uses an internal switch in the steering column as Timgr is talking about. Am I missing something here? Can't troubleshoot if we are not on the same page?

 

No, '75 is the last year for the bus column with the Sparton turn signal switch. '75 was the first year for the fuse panel. The '75 diagram is essentially the same as the '76 diagram, except for the steering column. '76 was the first year for the GM column.

 

OK was looking at the wrong year from the technical manual.

 

Well put.

 

Timgr...I do have a factory TSM. As you mentioned, the sparton switch is correct for my year. Another update, the rear park light problem has been solved. It was a loose wire at the rear wireloom connector. However, the other problems continue and the brakes still activate the front park lights. I'm still trying to figure it out with my test light.

 

You sure it's the front park lights coming on and not the front turn signal portion of the bulb? I would think you can disconnect the 4 way flasher switch and see if things normal up.

 

Here's where I'm at...
I have disconnected the hazard switch to take that out of the equation.
With the headlights off, all brakes/signals work (except hazards obviously)
With headlights on, and brakes on or off I get no left front or rear turn signal, a normal right front signal, and weak right rear.
To answer your question Walt, it is the turn signal portion coming on with the hazards connected and brake depressed.

 

Another observation...these cheap crown replacement front turn signals suck. The passenger side appears to function as it should. The drivers side has both filaments lighting up with headlights on. The "taller" filament flashes with headlights off. On the passenger side, its the "lower" filament which flashes. The gremlins are in full effect right now. I'm about to take some lighter fluid to the whole thing lol.

 

This happens when there is no ground to the fixture. Repair this and tell me results. We need to fix this one step at a time.
Can also happen if backfeeding happens.

 

The upper element of the 1157 is the park light portion and should not be flashing. Your wires need to be swapped around. This is providing the fixture has a good ground and not being back-fed.

 

My 2 cents on this - Yes verify the ground at the suspect rear lamp. Also check for a bulb having a crossed filament. I've run into that several times over the years. Sometimes a filament in the bulb will drop loose and contact the other filament, crossing up the electric circuit. Results could be dim lamp(s), two filaments lighting at once, blown fuse or lamps lighting when they should not.