Headlight problem
Thread Starter
|
Freshman User
Joined: Oct 2014
Posts: 27
Likes: 0
Headlight problem
I have a 93 f250 351 4x4 ..... The headlights will go out and come back on constantly while driving ..... I have replaced the headlight switch and the block that plugs into it but still have the same problem also it does not matter if its on dim or hi beam.....to my way of thinking it acts like a relay getting hot and opening and closing but i checked the relays in the power dist box under hood and none are for headlights .... Is there one somewhere else idk about.... Or any suggestions what to look for i am lost at this point... Thnks
Posting Guru
Joined: Aug 2004
Posts: 2,417
Likes: 4
From: Braham MN
Full headlight power goes through the dash switch, I am not sure where the hi low relay is but it would go through that too.
It's possible the daytime running light plug is giving you fits, it's on the front of the rad support, drivers side, just a few wires that end at the plug.
It's possible the daytime running light plug is giving you fits, it's on the front of the rad support, drivers side, just a few wires that end at the plug.
Posting Guru
Joined: Aug 2004
Posts: 2,417
Likes: 4
From: Braham MN
The wiring is in all trucks, they just put a shorting plug in place of the module and I 'think' all headlight power goes through it still.
Senior User
Joined: Aug 2009
Posts: 432
Likes: 0
From: Willow Grove, PA
check the plugs on the back of the HL bulbs, if the lock clip is broken they can vibrate loose. also check grounds going to lights could be broken in harness. Occurs when still, moving, bumpy, on long time or short, any & all?
Fleet Owner
Joined: Oct 2005
Posts: 20,783
Likes: 1,751
From: Kentucky
Each headlamp has a separate ground. If they both are flicking it is most likely on the supply side or common connector such as C202
Trending Topics
Fleet Mechanic
Joined: Aug 2015
Posts: 1,827
Likes: 358
From: Candy Mountain
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Fleet Owner
Joined: Oct 2005
Posts: 20,783
Likes: 1,751
From: Kentucky
Did you test the voltage going into then back out of the multi-function switch? I would suggest a simple test light since a high impedance DVM may give you phantom voltage readings since it does not load the circuit enough.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
You can isolate exactly WHERE the offending voltage drop is actually occuring by performing the tests outlined here:
http://www.aa1car.com/library/voltage_drop_testing.htm
It's easy! Don't let those automotive electrons scare you too much. The battery can cause trouble, but just be careful. Take your ring and watch off, and don't short the posts.
All that's needed here is a voltmeter, nothing has to be disassembled or disconnected. Anything more than a couple few tenths of a single volt on either side of a circuit is considered excessive. Since electricity always takes the easiest route, by bridging our voltmeter across any two points in parallel while the circuit is under load, the voltage being lost will show up there as a positive number.
From just the battery post itself to the battery cable terminal, or, all the way from the post to the headlight terminal, and everything in between, each connection that drops voltage adds up. This resistance is cumulative of course, and is ultimately what roasts switches and causes breakers to trip. Let us know what you find.
http://www.aa1car.com/library/voltage_drop_testing.htm
It's easy! Don't let those automotive electrons scare you too much. The battery can cause trouble, but just be careful. Take your ring and watch off, and don't short the posts.
All that's needed here is a voltmeter, nothing has to be disassembled or disconnected. Anything more than a couple few tenths of a single volt on either side of a circuit is considered excessive. Since electricity always takes the easiest route, by bridging our voltmeter across any two points in parallel while the circuit is under load, the voltage being lost will show up there as a positive number.
From just the battery post itself to the battery cable terminal, or, all the way from the post to the headlight terminal, and everything in between, each connection that drops voltage adds up. This resistance is cumulative of course, and is ultimately what roasts switches and causes breakers to trip. Let us know what you find.
Thread
Thread Starter
Forum
Replies
Last Post
HOODRAT
1967 - 1972 F-100 & Larger F-Series Trucks
8
May 30, 2012 06:14 PM
mycool88
1967 - 1972 F-100 & Larger F-Series Trucks
10
Mar 29, 2002 07:13 PM