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Discussion Starter #1
Hello all , after fixing my ignition cylinder issue truck was good. Then overnight i got up for a drink and looked outside to see my parking lights still on and dash lights on. They were off when parked. I replaced the headlight switch and when you have the parking lights on they are normal brightness but when you push the switch in to turn them off they only dim slightly and stay on. I disconnected the switch and the dash lights went out but the parking lights still stayed on. I have disconnected the battery and hooked it back up. The lights dont come back on when the battery is hooked back up. Any help would be great. I'm not sure where to go after the headlight switch. This issue literally just came out of nowhere
 

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Discussion Starter #2
Oh also I did note that the center pin think it had a brown wire going into looked a little heat warped too . I know that is common on these. Could something in the headlight switch Connector be shorting out possibly
 

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If it is not a Bronco, it's just not worth driving.....
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Is that swithc you put in to replace the old one a new switch? Sounds like you have a hot wire somewhere sending juice to your parking lights.

Start by pulling the switch back out and checking it really well for damage. Then put it back in and test the system.

If the parking lights are still on when they should not be, pull the fuse to your parking lights and see if they still come on. If they do, that means you have a hot lead somewhere feeding juice to your parking lights. You will have to trace individual wires to see if you can find any damage to them.

Electrical gremlins are the worst. Good luck
 

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If you pulled the switch and they stayed lit, the problem is not in the switch, although as stated it may be in the connector. Undoubtedly you have power crossing over through your parking lights to ground. Without looking at a wiring diagram, as suggested above, you may have an accessory recently installed that has a loose ground that it pulling it's ground through the parking lights. With a disconnected battery, and then reconnected, and the parking lights stay off, I wonder if you have something on a relay (like auxillary fog lights) that the relay is sending power to the parking lights and when you pull the battery cable, it de-energizes the relay?

You might start pulling fuses, and when the lights go out, at least you'll have narrowed down which circuit is involved.
 

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Discussion Starter #6
Thanks alot guys ! Today I'm going to replace the headlight switch pigtail and check fuses and check back after that. This morning when started the parking lights and reverse lights stayed on this time. Very weird
 

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I see from another post that you have a 1989.
The wiring diagrams for a 1990 should be the same.
See this link
1990 EVTM

On page 151-3 look for C134 listed in the graph location B 10

That connector is a common link for your back up lights and the parking lights.
I don't have a pin-out for that connector so I can't help beyond that. They do share a common ground. G100
 

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I see that in another thread that you had an issue with your igntion switch tumbler. Did you have to swap out your ignition switch?
I never had to do that so I don't know.. did you have to drop the steering column to do that? If so, I'm thinking that you pinched some wires putting it back together.
 

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Discussion Starter #11
Hey guys thanks alot for the help so far. I rechecked all the work I had done I did indeed replace the ignition switch and lock cylinder days prior. Last night turned truck off no light remained on. Weird. So this morning I went ahead and replaced the burned headlight switch pigtail and still good so far. all lights working as they should. Weird I knew the headlight switch and wiring would make lights not come on, but sticking on is a new one to me. Glad it's new now , having a 30 year old electrical connector that gets full 12v power will only last so many years I guess !
 

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Discussion Starter #14
Hello everyone, well unfortunately after a few days of relief my light issue is back. Noticed it this morning when I went to work and the lights were on again. Although the headlight switch pigtail did need replacing my issue remains. Although I do have new information. I checked the fuse number 4. No issues there. Checked the ground left side core support by headlight , okay there. But I did find an additional 14 gauge wire that ran from a passenger side ground at the firewall near the map sensor to the negative battery terminal where someone spliced it in with a. Existing black ground that goes into the harness along the core support. I cut the foreign wire while the lights were on and no change. Although now when I disconnect the battery and connect the parking lights instantly come back on. Also there is a ground strap on the right side firewall that isnt hooked up to anything. The same attaching point for the additional wire someone put in. Does this seem like I may be on the right track ? Or focus my attention elsewhere on the wiring ?
Thanks alot guys , this wiring stuff really does suck
 

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Yo Nally427,
Yes⚠⚠⚠😎
Troubleshooting; "...If you have a problem when turning on one circuit it causes another to come on partially (dim lights, etc.), check the ground for the part or system that was turned on first. i.e., if you press the brake pedal & the parking lights turn on partially or fully, check the brake lights' ground; This is caused by current going thru brake light bulb filaments & finding a ground in the parking lt. system instead of its own ground..."
 

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Discussion Starter #16
153138

Do any of you know what this connector is for ? I was checking grounds and saw the pins were loose on this connector took off the connector to inspect and pin broke and now the truck doesn't start. I'm assuming it has to do with the fuel pump as I dont hear it coming on at all. First the lights issue now this, when it rains it pours I guess. If I can identify what this connector is hopefully I can find a replacement
 

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1. that grey plug doesn't match up to the black one in the picture. The black one looks similar to the HEGO I don't have my truck anymore, so I can't check.
2. As Miesk5 explained, something that is poorly grounded is pulling it's ground through your lights. That loose grounding strap needs to be reconnected. Probably from the firewall to the engine. The body, frame and engine should be all connected by way of cables or straps. A quick and dirty check to see if the loose strap is the problem, you can use a jumper cable and connect it to the battery negative. Regardless it needs to be connected.
 
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