Headlights Cutting Out, Need Help Troubleshooting

'91 XJ, been having issues with my headlights cutting out randomly.

After the first time the lights cut out on me (almost a year ago) I replaced the hi-low switch, which was slightly melted, and didn't have any problems until recently. Now, within the last 2 weeks the headlights have cut out once while driving, and another time just would not turn on. Every time this has happened I've been driving with the headlights on for 2.5+ hours. The parking lights illuminate & turn signals work normally, all fuses checked out good, so I checked the headlight switch- the rearmost terminal is cooked & the corner or the wiring connector it plugs into is totally melted. So, I'l be replacing the headlight switch & wiring pigtail, and then installing an upgraded headlight harness using relays & heavier wire to take the load off the switch. I know the factory harness is the usual weak point in the XJ headlights & the new harness should eliminate the most likely failure point.

The catch is that I also have a problem with my parking lights- the driver's side parking lights don't illuminate, but they do work as turn signals. This has been a problem for a while now that I've just been ignoring, but now I have to wonder if it has anything to do with the headlight issues. I'm not running higher than OEM wattage bulbs in anything, and haven't had any fuses blow for any of these circuits. I'm wondering if the headlight switch connector melted purely due to the prolonged load of the headlights being on for a few hours (which apparently is not uncommon, based on how many threads I found where people had this issue); OR if might I have a short in the parking light wiring somewhere. I assume that full power for the parking lights runs through the headlight switch, like it does for the headlights?

I think I need to find out what circuit the cooked headlight switch pin is a part of. If it's for the headlights the new harness should take care of it, but if it's for the parking lights I'll know I need to look for a short. Does anyone have wiring diagrams for the headlight switch & the connector under the hood near the airbox?

The XJ headlight wiring is less than OK. Burned switches, and melted wires or wire plugs are from wires that are too small.

The other lighting issues may or may not be related. Corrosion in the light sockets and corroded/damaged wires and ground connections are also common.

Install a new headlight switch and an upgraded headlight wire harness.

Inspect the rest of the lighting system, bulb sockets and wires and replace anything sketchy. Disconnect and clean the wire plugs and clean the ground connections.

I checked the bulb sockets & easily visible wiring when the driver's side front parking lights first stopped working, but everything looked OK. One thing I noticed was that I definitely have some corrosion in the big connector near the airbox. I cleaned it as best I could with electronics cleaner & a toothbrush, but I think it's too far gone to be a good connection at this point. I was thinking I'd replace the single connector with a couple weatherpack terminals.

Does anyone know where I can purchase a *new* headlight switch connector/plug/pigtail for my '91? I found one for '92-'96 XJ's but nothing for mine.

From looking at Napa's part fitment guide, apparently they changed the switch in '92. Looks like '84-'91 XJ's used an AMC switch, '92-'96 used a Chrysler switch that apparently is a much more common design. So despite '91 being the first year of the XJ as a Chrysler product, and having the the H.O. engine, etc., they carried over the AMC switch... damnit. I'm guessing the pins are different and the connector will not swap over, otherwise the guide should show it as fitting (RockAuto's fitment guide shows the same info as Napa's so I assume it is correct...).

Ugh... I'll get one from the junkyard if no new replacement exists but I would much rather pick up a new one....

I had a similar problem where the headlights wouldn't work. replaced the headlight switch to no avail. It turned out to be the turn signal / high beam switch.

In my case, I could wiggle / switch the high beam switch, and sometimes I could get the lights to work for a short time.

Be sure to order the right switch, depending on if you have variable wipers or not.

David Bricker / SYR

You mean you replaced the actual turn signal / windshield wiper switch stalk (I think it's called a multi-function switch)?

I replaced the switch on the steering column that controls the high/low beam selection as it was slightly melted looking after the first time the headlights died on me while driving. I'll check it again when I attempt replacing the headlight switch & connector this weekend.

Red91Laredo said:

Does anyone know where I can purchase a *new* headlight switch connector/plug/pigtail for my '91? I found one for '92-'96 XJ's but nothing for mine.

From looking at Napa's part fitment guide, apparently they changed the switch in '92. Looks like '84-'91 XJ's used an AMC switch, '92-'96 used a Chrysler switch that apparently is a much more common design. So despite '91 being the first year of the XJ as a Chrysler product, and having the the H.O. engine, etc., they carried over the AMC switch... damnit. I'm guessing the pins are different and the connector will not swap over, otherwise the guide should show it as fitting (RockAuto's fitment guide shows the same info as Napa's so I assume it is correct...).

Ugh... I'll get one from the junkyard if no new replacement exists but I would much rather pick up a new one....

Click to expand...

The plug is same as Ford.

You need to do the harness upgrade. About $35 and takes 1/2 hour to install. Lights will be 35 to 40% brighter as a bonus and you'll never need to replace a headlight switch again.

I read that somewhere else as well, do you know what model Fords used the same plug? I already got a good one from the junkyard and replaced it, but would be cool to know for future reference. I found that my high/low switch ("dimmer switch") had a burnt terminal again and it's plug was also slightly melted, so I replaced those too.

I'm pretty sure that these problems are the result of installing H4 housings with 60/55W bulbs- I didn't realize the H6054 sealed beams that XJ's originally came with only have 35W low beams. I did run these bulbs for about a year of normal driving without any problems (i.e. no nighttime drives over 2-3 hours long); until I took a road trip and had been driving for several hours after dark, which was the first time the headlights cut out while driving. I also found that my headlight plugs were somewhat corroded, which may have also contributed to the issue (corrosion = increased resistance = more heat = melted components, at least that's my theory).

Had I realized the H4 bulbs have higher wattage low beams than stock headlights I would have DEFINITELY installed the upgraded harness at the same time, and I would STRONGLY urge anyone else installing conversion housings with H4 bulbs to do the same. Although you may get away with running the H4 bulbs on stock wiring for short drives, the two upgrades really need to go hand in hand. The XJ headlight wiring is marginal to begin with, add 10 or 20 years worth of corrosion, and bulbs that are 20 watts higher than the wiring was designed for, and you are just asking for trouble. Trust me, having your headlights cut out while you are going 70 mph down a winding highway in the middle of nowhere is NOT something you want to experience.

I am getting everything together to make a really beefy headlight harness using relays and 10 gauge wire. So I can safely drive at night in the meantime, I'm going back to stock-speck H6054 sealed beams and replacing the headlight plugs (though true high-current H4 plugs are hard to find, stock replacement ones are readily available and dirt cheap).

While troubleshooting all of this I found that my driver's side parking lights have been out simply due to a loose wire, not sure why I didn't find it before but I guess I just didn't look thoroughly enough. So that issue was just an unrelated coincidence. That being said, I have a little corrosion in my 10-pin connector (the big square one near the airbox), so I will be replacing that too, probably with some Weatherpack terminals that should hopefully be more corrosion-resistant.

70s and 80s Fords, I think.