engine dies when headlights on [Archive] - FSB Forums

: engine dies when headlights on

04-17-2006, 01:34 PM
Did a search but pulled up 2 results and did not fix the issue.

I have a 93 XLT Bronco 351W 5.8.
4 inch procomp lift, 35 in tires, 4:56 gears

My problem is this, whenever I go to turn on the headlights, the engine dies. I just had a new Optima (yellow) battery, and new alternator from fordfuelinjection and starter solenoid installed professionally.

The Bronco drives fine untill I go to pull the headlight switch - then it just dies. The stereo, interior lams and even my off-road lights work fine.

I had the codes checked with no codes being thrown. I checked all the fuses and they look good.

I'm not sure where to go from here. Anyone else ever have this issue. Thanks for your help in advance.

04-17-2006, 02:16 PM
The professional who installed your stuff obviously did something incorrectly. There has got to be a short somewhere in your system or a bad ground maybe.

04-17-2006, 02:34 PM
Your bronco has photophobia...

Ok seriously. Do the headlights actually turn on when you turn them on? that could help you track the short. if its just when you turn on the parking lights but not the headlights it could help you where to look. If it turns off as soon as you turn on the parking lights (or even touch the switch) you're ignition or something else in your steering column is grounding out through the lights. you know that little circuit that makes the chime go off if you leave the keys in the igniton or the lights on..... Just some places to start checking.

edit: do the 93's have the headlight switch on the dash or on the column stalk? (with the turn signals etc)

04-17-2006, 02:42 PM
I had the exact same problem with my 96. I had it in the shop this past Thursday and Friday. They claimed they couldn't find anything wrong. My truck would hesitate when I took off after a cold start, too. They said they tightened the battery cables, ran diagnostics, checked the electrical system, ignition system, and the fuel system, and fixed a small vacuum leak. It doesn't turn off anymore when I turn the lights on, and it hadn't hesitated all weekend, but did again today when I left for work, then when I went to lunch, and again when I came back from lunch. So I'm a total loss...

04-17-2006, 02:49 PM
Check you're battery cables. Make sure they are tight on the terminals, and that the ground etc. is tight to the chasis and clean (free of rust). Have your battery load tested. I bet thats where it is. also check where it connects to the alternator and the power dist. box and the starter relay

edit: by battery load tested, dont put the load from one terminal to the other, but thorugh the chasis electrical system.

04-17-2006, 04:31 PM
I had a similar problem, sounds like the ground to me dude. Also check your starter solenoid and make sure it's installed propperly

04-17-2006, 06:54 PM
The cables are in good condition, but l will double check the cables tonight after work. The engine quits when the parking lights go on, however, when the switch is pulled all the way, the headlighs come on too - no dimming either. The headlights swithc on my 93 is on the dash.

Smileybry - how does my bronco pic have photophobia??? :crazy

04-17-2006, 07:37 PM
Check and clean the ground wires that go to the rad support and/or the fenders,also make sure the battery cables and battery terminals are clean,as well as the neg battery cable to frame and block.

04-18-2006, 09:53 AM
Smileybry - how does my bronco pic have photophobia??? :crazy

Photophobia= fear of light

you turn them on, it gets spooked and shuts down...

Ok seriously..it sounds like you have a load problem in your power system. Lights pull a decent sized load. They start pulling juice, and your engine (or computer or something else) gets none. crazy idea but unhook all your lights (or light bulbs) then turn the switch on and see what happens.. just to see whats what. With these unhooked, if your engine still shuts off then you have a short through your lights...if it stays running its a load issue..maybe..i dunno its early

04-18-2006, 02:53 PM
Oh, gotcha smileybry when it comes to the photophobia.

It's fixed. It was a loose ground near the passenger headlight. No more problems, thanks to all for the input! :rockon

04-18-2006, 02:57 PM
Oh, gotcha smileybry when it comes to the photophobia.

It's fixed. It was a loose ground near the passenger headlight. No more problems, thanks to all for the input! :rockon


08-05-2007, 08:19 AM
UPDATE: figured out which ground it was. In case anyone else comes along with same problem it is the ground post on passenger side nearest the headlight. Despite appearing tight on the outside, their is a nut on the backside that cannot be seen. if it is loose at all, it will cause this problem. Mine only required a few turns to tighten up but now idle issues are fixed, engine runs with headlights on.

Got the same problem now after the alarm install on 95 xlt 5.8. Looked all over for grounds near the headlights but not seeing any that look suspect. Was curious if there is a ground chart anywhere showing where major grounds are located under the hood? When you pull the headlight switch you can feel the relay click over and then it dies. Makes me think there is a short somewhere around/under the relay/fuse box under the hood but I haven't been able to find it. It also will hesistate when cold. Voltmeter on the fuelpump goes to zero volts once the headlight switch is pulled. throwing no codes.

Ruthless69 if you are out there, send me a quick PM so I can check the same ground that you found loose.


01-23-2010, 01:24 PM
I also had this same problem...After replacing and fixing various battery wires and headlight switch I found this sight and checked out that loose ground on the passenger side...seems to have fixed the problem. Thanks!!

01-31-2010, 04:49 PM
Buddy had the exact same problem the ground strap from block to frame was loose. So the block was grounded but anything that grounded through the frame didn't work and would drop the voltage. Cleaned and tightened the connection and it was all fixed.

02-04-2010, 04:29 PM
ad an 83 f150 do the same thing. it was a bad gound from the motor to the frame.the lights pulled the juice from the ignition system. sad to say but i fought it for weeks and a chvey mechanic told me how to fix it lmao

02-16-2010, 06:32 PM
I've gotta add one more here, mine was doing that, but it was all going dead when i turned a curve to the right.... after monkeying around with everything, turns out my dumb a$$ put the battery in on top of a few wires (can't remember what they were), after not very long the battery weight caused them to get rubbed bare, so every once in a while they would short and cause all kinds of problems. For anyone else searching this thread, make sure your battery isn't on top of these wires, they kinda try to fall down there under the battery if you remove it so it's an easy mistake if you don't pay attention...

*** ready to take my medicine now ***

02-08-2013, 11:40 PM
Yeah, I'm reviving an old ass thread. But only to say that you guys kick ass yet again. totally salvaged a beach camping weekend with this info!!