Headlight issues! Common switch problem? Harness problem?
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Headlight issues! Common switch problem? Harness problem?
Hello, I have an 88 F350 7.3L diesel that we've been working/restoring. I hear that these model fords are horrible when it comes to the headlight switch. The truck has the common problem of "finding the right spot". When you pull the switch all the way out, the headlight comes on, but no parking lights. So you have to push in ever so slightly to find the spot where all the lights come on.
Figuring the switch was bad, I pulled another switch from a junk truck we have. When I took my F350 apart the wiring harness was badly warped from head. So I also replaced that off the donor truck. I have no idea if the switch was good or not, but worth a try.
Sure enough the headlights were still having the same problem of "finding the right spot". So I figured "hey this switch is bad also." Common Ford problem.
So I ordered a new after market switch of Ebay. Install it yesterday, and same problem of finding the right spot. VERY fustrating.
Does anyone still think the switch is the problem??? Possibly got a bad new switch??? Or is there another common problem that is causing this??? Any imput would be GREATLY appreciated! Thanks in advance.
Figuring the switch was bad, I pulled another switch from a junk truck we have. When I took my F350 apart the wiring harness was badly warped from head. So I also replaced that off the donor truck. I have no idea if the switch was good or not, but worth a try.
Sure enough the headlights were still having the same problem of "finding the right spot". So I figured "hey this switch is bad also." Common Ford problem.
So I ordered a new after market switch of Ebay. Install it yesterday, and same problem of finding the right spot. VERY fustrating.
Does anyone still think the switch is the problem??? Possibly got a bad new switch??? Or is there another common problem that is causing this??? Any imput would be GREATLY appreciated! Thanks in advance.
Post Fiend
Joined: Nov 2003
Posts: 21,285
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From: Nutter Fort, WV
The problem is the wiring is not heavy enough.
The best fix, new switch, new connector for the switch.
Now before you fry the new switch, do the headlight relay mod and never have problems again.
This is an article that details the process.
Whiter Whites, Brighter Brights .: Articles
The brighter lights are an added bonus.
The best fix, new switch, new connector for the switch.
Now before you fry the new switch, do the headlight relay mod and never have problems again.
This is an article that details the process.
Whiter Whites, Brighter Brights .: Articles
The brighter lights are an added bonus.
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I bought another new switch from advanced auto. Still same problem. So I find it hard to have 3 straight bad switches. I replaced the pigtail connector that goes into the headlight switch. So I don't believe the problem lies in the switch or connector. I traced back to what i think is the parking light relay, but i dont think that's the problem either.
Back to Dave Sponaugle's previous article post it says that the headlight thermal breaker goes bad. Could these be the problem?
One other thing to mention, is the truck has the 7.3l diesel, and when you turn the key on for the glow plugs, the rear tail lights come on. There's juice feeding through some how. Not sure if this is related to the same problem, so I'm throwing it out there.
Back to Dave Sponaugle's previous article post it says that the headlight thermal breaker goes bad. Could these be the problem?
One other thing to mention, is the truck has the 7.3l diesel, and when you turn the key on for the glow plugs, the rear tail lights come on. There's juice feeding through some how. Not sure if this is related to the same problem, so I'm throwing it out there.
Postmaster
Joined: Apr 2008
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You have a burnt-through or rubbed-through harness somewhere, the tail lights should only come on with the main lights switch, and never on their own but always together with all the other running lights. I once worked on a passenger car that had the main lights switch melted cause of hooking up to a trailer that lit up like a Christmas tree, one of the wires in the harness was burned up and bare of insulation some ridiculous distance from the switch, like a foot or something, I had to fish the entire harness out from under the dashboard to repair it and even so I barely had enough space at the end of the insulation - maybe you have a similar issue, with the harness damaged further away from the lights switch where it's hard to see it?
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Post Fiend
Joined: Nov 2003
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From: Nutter Fort, WV
Does it have a 7 pin trailer plug?
Power wire to the 7 pin plug is shorting to the tail light circuit when you turn the key on.
Power wire to the 7 pin plug is shorting to the tail light circuit when you turn the key on.
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Finally traced the problem and got it corrected. The glowplugs were feeding throug the tail lights b/c my dad had a hot wire shoved into the fuse box. Some how that was causing it to feed through.
As for the headlights, there was a fuse missing from the fusebox, but that wasnt the problem. I another fuse more closely that had to deal with the tail lights, and the fuse was half way burnt. I guess where it wasnt burnt all the way through it was letting enough current to pass, but just not function correctly.
Hope this thread helps anyone else with the same problem. Check for a semi burnt fuse.
As for the headlights, there was a fuse missing from the fusebox, but that wasnt the problem. I another fuse more closely that had to deal with the tail lights, and the fuse was half way burnt. I guess where it wasnt burnt all the way through it was letting enough current to pass, but just not function correctly.
Hope this thread helps anyone else with the same problem. Check for a semi burnt fuse.
Posting Guru
Joined: Dec 2009
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From: Dairy, OR
Scooter make sure and do the relay mod that Dave & Rupe mentioned. I have had to do the mod to every ford truck I have owned over the years. A few dollars in relays and an hours worth of work will save you tons of headaches down the road!
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