1978 Jeep CJ7 Tail Light and Turn Signal Problems

  • 1978 JEEP CJ7
  • V8
  • 4WD
  • 115,000 MILES
When I turn the head lights on, while the turn signals are on, the signals quit working. Should there be Continuity between the tail light wire and the ground with everything off? I Have Power at the socket with the signals on, but when I put a bulb in it doesn't work.
Do you
have the same problem?
Thursday, July 29th, 2010 AT 10:02 AM

1 Reply

See my profile.I am not a "paid mechanic" nor am I paid here. Investigate last CJ 5/7 forums (from the last year) You will see how far I will go, to assist you!

This is my hobby, and I know CJs well.

I need MORE info, in order to help you. I cannot see or test, you will have to do so for me. If you do not understand something. STOP and ASK, before something bad happens!

I may get out of order, but bear with me, I will attempt to help you all the way, AND YOU WILL NOT GET A MORE "PERSONALIZED" answer than mine.

This sorta problem may take time, but I will hang with you.I try to answer quickly (sometimes we might work on this for several days), so we can get you going faster! The more info from you the better.

Without just an outright wire cross, THERE IS ONLY a few ways (other than a dying battery) That the headlights or Park/ Tail lightsCOULD AFFECT----The turn signals.

One is: ----the Flasher element and the running light element of Your Dual Element Bulbs (park and/or tail bulbs, to include side marker lights) Are crossed somewhere--some how.

What I mean is something has one or more of the sockets or wires crossed.

The head light switch has 2 SEPARATE circuits---headlights only is one, with only one position.

Tail and park running lights is the other circuit (but with 2 positions) THEY DO NOT CONNECT TO THE HEADLIGHTS!

Your turn signals are yet another 3rd Circuit---separate from the other 2.

Things ----COULD HAPPEN----To cross flasher(ing) circuit to the Park/ tail light circuit.

One is, A dual element Bulb installed incorrectly and TOUCHING BOTH "SOCKET PINS" AT THE SAME TIMEINSTANT 2 CIRCUITS CROSSED!---Or a Socket in bad condition allowing the 2 pins to touch inside.

Remember the 2 pins in the socket are 2 separate circuits----1 is "signals" the other is "running lights"----the socket itself is GROUND.

Do not forget sidemarkers may be in the equation!

Answer these below, do some testing if you can, and we may be able to start Isolating Stuff.

1) Has anything been done to your rig (when this COULD HAVE STARTED) Like (new) trailer lights, hooked to a trailer wired incorrectly. ETC?

Wild-Donkey 4 wheeling in brush/rocks?

2) Do you have a voltmeter and/ or 12 Volt test light? SKILLED IN THEIR USE WITH 12V or continuity tests?

3) Are all TURN SIGNAL BULBS INSTALLED CORRECTLY?(EZ to accidentally CRAM 1 in 180 degrees out!)

4) anybody recently mess with the wiring?

5) Do all turn signals REACT THE SAME WAY, when Headlights (or anything for that matter) is turned on?

EXPLAIN EACH'S DIFFERENCE IN OPERATION if they do operate different (FL blinks once and explodes, RR Smokes and blinks fast EX. EX. EX.)

6) When turn signals flash, are they brighter than the tail lights or park lights (Which doing what?)

7) Do the park or tail lights dim out bad, while flashers flash?

8) What does hazard flashers do to each signal or park/ tail light?

9) Remove park and flasher bulbs on the grill (side marker bulbs on front too). What does rear do?

10) Remove tail lights (and rear side marker bulbs). Reinstall the grill lights. Test system, WHAT HAPPENS UP FRONT?

Enough for now. Send DETAILED RESULTS!

Waiting on answers----all questions


The Medic
Was this
Thursday, July 29th, 2010 AT 6:34 PM

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