Parking/Running lights short? | Ford Explorer Forums - Serious Explorations

  • Register Today It's free!

Parking/Running lights short?

nodoorpanel

New Member
Joined
June 17, 2011
Messages
5
Reaction score
0
City, State
LALA
Year, Model & Trim Level
91 XL
Hi everyone new member here. I tried asking this question in an old thread but didn't get any replies so I figured I'd try a new thread.

I just got 91' explorer xl and and having an issue with the lights, and can't drive it @ night til I fix it. Here is the problem, I hope someone can help.

My headlights, high beams, reverse lights, brake lights and turn signals all work. The problem is none of the parking/running lights work, front or back. As soon as I put a new fuse in slot 11 it blows instantly. 11 is for the parking/license plate lights according to a pic of the schematic. Also, one of the license plate lights is missing a housing, bulb and just kinda hanging out the hole, its not frayed anywhere though. I assume there is a short somewhere? Any help on where to start would be a huge help. I bought the haynes repair manual for it so i have the wiring diagram if that helps.
 



Join the Elite Explorers for $20 each year.
Elite Explorer members see no advertisements, no banner ads, no double underlined links,.
Add an avatar, upload photo attachments, and more!
.





First off I would remove the park/turn bulbs and make sure some rocket scientist hasn't forced a single contact bulb into a double contact bulb socket. If not then you'll need to start unplugging the lights, one at a time, and see if it blows a fuse after each disconnection. If that doesn't uncover the problem then you must have a wire worn through the insulation and grounding out......not fun to find. Make sure someone hasn't rigged a trailer plug connection into the harness in the back.
 






I would check for trailer wiring... sometimes that gets done with a razor knife and duct tape and over time, it shorts out. Look through the jack compartment for any obvious hacking.

The easiest way to solve this, unfortunately, is with a factory manual because it tells you where the wires run and connectors you can disconnect to isolate the problem. For example, there is probably a master connector on a fender for all the front lighting. By disconnecting that, you can figure out if the front lighting is at fault or not. Anyway, that's the general idea.

Edit: +1 on the bulbs, I don't know on the 91's but the 94's use this thin rectangular base design... I have had nothing but headache from it. For what it is worth, if you replace these bulbs, try to get the ones with the plastic base, not the molded glass base. I have found the glass base ones to be unreliable in the aging sockets.
 






Thanks for the replies. Before I posted yesterday I went through and replaced all the rear bulbs. There was a double filament where a single should have been (rev) but after getting all the right ones in the right places the fuse still blew. I'm gonna go through and do the front ones today and replace the lic plate one. Then take it from there I guess. Electrical problem are the worst.

I don't have the factory manual to look for the master switch. Can I find it in the haynes?
 






You may not appreciate this right now, but it's worse if it is intermittent. At least you do have a chance of pinning it down, given enough fuses.

Also not much help today, but I will be in a position to post schematics and connectors for you next week. They will be for the '94, and I have no idea if they held the same wire colors or not.

I forgot something else: Do you have an aftermarket remote starter or alarm? If so, you might look around for wire hacking under the dashboard.
 






There is no trailer hitch, alarm or even radio. so that's a good thing as far as isolating the problem.

*update*

checked and changed the front parking bulbs and the license plate bulbs. Fuse still goes instantly. Got a connectivity tester and obv have power to fuse slot 11. Now how would i got about isolating where the potential short may be? I have the chassis electrical diagram in the haynes manual.
 






Short Detector

Make a Short Detector from a old Seal-Beam Headlamp or a 1157 Dual Filament Bulb/Socket (Tie-each filament in parallel). Solder or crimp some male terminals on the two wires from the lamp and insert them in place of the fuse. If the Short is Present, the Lamp will be on "Full Intensity." Unplug each branch circuit to the individual lamps one at a time. If the Lamp turns off, you have found the suspect branch circuit. This method is better than constantly inserting new fuses. Good Luck
 






Ok, let's try this... trying to help now, but these are going to be for the '94 and so I will generalize as much as I can but just be aware.

Key Off and headlight switch off for this entire procedure. We are doing all of this by breaking connectors and measuring for the short, so you will not be replacing fuses in this procedure. If your probe measures 12V only then you need to do the short detecting light trick like Robert says, and use the connectors I describe below as isolation points. Read this whole post because I edited all over the place and you need to understand the whole thing.

Go to any front bulb, probably the parking on the driver side is easiest. If you test continuity to ground right now, both the brown and black wires should be grounded if you are blowing fuses. The black wire IS ground, but the brown one should be switched 12V+. The best isolation point for this branch is the giant firewall connector near the brake master cylinder, this connector is called C147. Break this connection and see if the brown wire is still grounded. If so, the short is from the firewall forward. Breaking this connection also breaks the supply to the switch, so you will not be blowing fuses with C147 open because it supplies power to the headlight switch (and pretty much everything else in the dashboard). C147 may be difficult to get open, it is the largest jack on the vehicle with the most pins. If you cannot get this connector open, you will have to cut the brown wire on the firewall side to test and then splice it again when you are done. Not a big fan of this, it's just plan B...

Going to the rear, the first isolation point sucks because it is high in the dashboard. So, let's go past that and do an easy one in the back. Open the jack compartment, and look for a connector with a brown wire. The same procedure applies going back with one little twist. Opening this connector (C307) isolates all the back lights EXCEPT the right rear parking light, which... grrr! connects at C307 on the supply side of C307. So, if the firewall connection is open and C307 is open, and you measure ground on the brown wire of the back right bulb, you have a short... somewhere between the bulb socket and the headlight switch.

I'm sorry this is convoluted, it is like trying to describe a picture with words, and I am pushing something personally to get this information posted tonight. This information is bridged across many pages of the schematic so it's not something easily scanned. I will be hoping you find it in the front, it is the easy fix. And giving you just enough information to confuse, I'm sorry to say I will have limited internet access from now until Thursday. If there are quick yes/no's, I can help. For a what next question, I will probably have to defer until then.

Best of luck, I'll be hoping you find it early.

Also, if you were to set up the short detector Robert talks about, then you would just do what he said, turn on the lights and break/make the above connections. Augh! except you can't use the firewall connector as an isolation point because it supplies voltage to the switch, so with the short detector, you must cut the brown wire to isolate the front. If the short detecting light goes out, you are following the short. If your connectivity tester detects 12V, you can put it where the fuse goes. If you can't measure resistance, then the short detector is how you need to go. This is all pretty straight forward logic, once you know where the connectors are to isolate things. The wire that is shorted is the brown one, if it is like the '94.

Gotta go, hope this makes a tiny bit of sense.

~Phil
 






This may sound REALLY stupid, but then again maybe not..... could it be the master headlight switch?

Granted my troubleshooting is more on 24v military crap, but we've had issues like this and it would wind up being the master headlight switch 80% of the time.
 






It sure could. If it were broken internally in some way, it could. The thing is, I think 90% of these problems are aftermarket wiring, trailer harnesses, alarms, remote starts, everything that reduces the integrity of the wiring.

I think, in this case, we have ruled that out because there isn't any such accessories. That trailing 10% can be hard to find unless you have experience and good knowledge of chassis wiring.
 






Mr. cribb-Is the headlight master switch part of the multi function switch?

roadrunner-By breaking the connection do you mean literally cut the wire? Will I be able to do your method with a simple connectivity tester?

I saw that there is a 1991 explorer EVTM book for trouble shooting electrical problems and it had a chapter on fuse 11. Which is the one i'm having problems with. If anyone has access to that book and could scan/upload that chapter or any that might relate to the parking lights it would be greatly appreciated.

I'm gonna be out until later, then back here to work on isolating the short. Thanks for all the help and i'll keep you posted.
 






In almost all cases I mean just open the male/female parts of the connector. There are 2 cases where you may have to cut a wire:

1. If using the short detector light in the fuse socket, you will have the headlight switch on. So, power flows through the firewall connector to the headlight switch and back out through the same connector to the front lights. You cannot open this connector to isolate because you will loose power to the switch, defeating the test. In that case, you would have to leave the connector intact and cut the wire to test.

2. If you are using the resistance to ground technique and cannot get the firewall connector apart (it is big with a lot of contacts and unknown goop sealing it) then it may be easier to cut the wire to test and then splice it again. I say this easily because I have cut and spliced a lot of wires in my days and I know the tricks to making it a lasting repair.

Yeah, the EVTM is the exact book you need for this.

The multifunction switch is the left stick on the steering wheel column, turn signal, high/low, wipers. The headlight switch is in the dash, of course.
 






These are from 94, note differences, like the fuse is #10 instead of #11. The 2nd page is for 2-door, and the 3rd page is for the 4-door. I can post more scans Tuesday night if you tell me what you need. Sorry it's not a '91, hopefully it's close!

91-0001.jpg


91-0002.jpg


91-0003.jpg
 






Mr. cribb-Is the headlight master switch part of the multi function switch?

referring to headlight switch on dash under left side vent.

In the military we call it a master light switch because it controls blackout lights for the use of night vision goggles.... sorry to confuse you.
 






Hi everyone new member here. I tried asking this question in an old thread but didn't get any replies so I figured I'd try a new thread.

I just got 91' explorer xl and and having an issue with the lights, and can't drive it @ night til I fix it. Here is the problem, I hope someone can help.

My headlights, high beams, reverse lights, brake lights and turn signals all work. The problem is none of the parking/running lights work, front or back. As soon as I put a new fuse in slot 11 it blows instantly. 11 is for the parking/license plate lights according to a pic of the schematic. Also, one of the license plate lights is missing a housing, bulb and just kinda hanging out the hole, its not frayed anywhere though. I assume there is a short somewhere? Any help on where to start would be a huge help. I bought the haynes repair manual for it so i have the wiring diagram if that helps.

***!!!
I have this same EXACT Problem with my 91 Ford Explorer XL. I read through all the thread replys and I will be sure to check out my 'master light switch' ( even though its just a rod because the plastic piece is MIA l0l ).
:thumbsup:
 






r3d.... when you check the light switch, separate the wiring harness from the switch to see it the plastic is burnt. I hope it's not, because splicing in a new wiring pigtail for the light switch isn't fun at all. I picked up both the switch and wiring pigtail from the junkyard to repair mine.

I had to do this after my ignorant fog light wiring I did, burned up my light switch.

Another good spot to check is in the drivers side kick panel (by the parking brake) pull that panel and that is where a couple ground wires are. Check there to make sure after 20+ years it hasn't wiggled loose. I think the light switch ground is there, but can't remember for sure.
 






quick resolve - blowing fuses? bypass fuses... a little wire with poor ingenuity - and veua'la' I have all my lights working. nothing burning, i can tell i have a few shorts because my 4x4 button and low range button dont do anything but make my voltagemeter drop when i push em
 






I have a similar problem, the complete opposite. I have corner lights, taillights, third brake light and reverse lights. I have no headlights no brake lights no blinkers no rights and no windshield wipers.
 






quick resolve - blowing fuses? bypass fuses... a little wire with poor ingenuity - and veua'la' I have all my lights working. nothing burning, i can tell i have a few shorts because my 4x4 button and low range button dont do anything but make my voltagemeter drop when i push em

Sounds like a broken wire or maybe more. It's not recommended that you continue to run your lights like this, or you might wind up with a mess on your hands.
 



Join the Elite Explorers for $20 each year.
Elite Explorer members see no advertisements, no banner ads, no double underlined links,.
Add an avatar, upload photo attachments, and more!
.





I have a similar problem, the complete opposite. I have corner lights, taillights, third brake light and reverse lights. I have no headlights no brake lights no blinkers no rights and no windshield wipers.

I'd check your fuses, or even the ground wires.
 






Back
Top