on them for around 10 bucks.
odd taillight problems
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Elder User
Joined: Feb 2015
Posts: 676
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From: south east kansas
odd taillight problems
i have a 1973 f100 my truck currently has one 73 taillight and one 74-79 taillight, one side won't come one when i hit the brake, however all other functions for that side will come on. it is not the bulb. if i giggle the fuse for it it switches to the other side, i do not have a fuse in it currently just a piece of metal( is this the problem?), i wonder if its a bad brake switch or maybe the hazard relay thingy( the think that ticks). i'm kinda stumped on how to fix it.
Hotshot
Joined: Apr 2009
Posts: 14,333
Likes: 247
From: Stanley, VA
No, it's not a bad brake light switch. If the switch was bad, it would affect both brake lights not just one. It's not the flasher either, again, if it was, it would affect both lights.
You're saying both sides are affected alternately, switching sides when you jiggle the fuse?
Do the turn signals function normally?
You're saying both sides are affected alternately, switching sides when you jiggle the fuse?
Do the turn signals function normally?
Laughing Gas
Joined: Apr 2001
Posts: 868
Likes: 3
From: New Glasgow, Nova Scotia
You have a bad pin in the tail light socket assembly more than likely. As said , it's not the switch or fuse if the other side works. This is a common fault and they sell new sockets with 6 inches or so of wiring on them for around 10 bucks. I always have 1 kicking around just in case. Only other possibility is a break in the wire running from front to back. Probe the wires at the taillight before going under the truck. And yes, a piece of metal in the fuse is a bad thing. If you had a short you could start a fire pretty easily.
Junior User
Joined: May 2016
Posts: 68
Likes: 0
Check to make sure the wires are connected properly on the socket. I had some odd tail light behaviors that I finally tracked down last week. The PO had swapped the passenger side socket for an aftermarket one. He obviously didn't bother to look at the other socket or a wire diagram to see what wire went where. basically the power wire was in the ground position.
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Elder User
Joined: Feb 2015
Posts: 676
Likes: 0
From: south east kansas
No, it's not a bad brake light switch. If the switch was bad, it would affect both brake lights not just one. It's not the flasher either, again, if it was, it would affect both lights.
You're saying both sides are affected alternately, switching sides when you jiggle the fuse?
Do the turn signals function normally?
You're saying both sides are affected alternately, switching sides when you jiggle the fuse?
Do the turn signals function normally?
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
Check your grounds, most elec issues on these trucks are usually related to a bad ground. Also do not rule out the tail light sockets, they are notorious for going bad.
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Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 783
From: Simi Valley, CA
1973, 1974 F100/350 Stylesides before serial number T80,001 have metal tail lamp bodies with separate lenses that attach with Philips screws.
The socket w/wires is swaged into the metal body, so it cannot be replaced.
1974 F100/350 Stylesides from serial number T80,001; 1975/79 Stylesides; 1975/91 Econolines & 1978/79 Bronco's have one piece molded plastic tail lamps with separate sockets that twist into the bodies.
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Elder User
Joined: Feb 2015
Posts: 676
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From: south east kansas
yep my driver side( the one that does not work right) is metal, and the pass side is the plastic. so if the driver side socket is bad i either need to find one or switch to the 1974 F100/350 Stylesides from serial number T80,001, style. wild idea here could my chunk of metal be causing to much resistance to the point only one brake light comes on?
Fleet Mechanic
Joined: Sep 2014
Posts: 1,626
Likes: 78
From: NE Texas
Depends on how conductive the metal is. Like above, put a fuse in there first (what do they cost, a buck?) and start checking to make sure your grounds and socket connections are good. It is not uncommon to have a great connection when you test the wire to the socket and a crap connection IN the socket. Fuses and sockets are cheap, fires are expensive. It is possible once you fix this that you may see turn signal issues - that would indicate the socket grounds are iffy, which is VERY common. If so, be sure to check contacts and grounds at the front lights too - they are also in the turn signal circuit.
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Elder User
Joined: Feb 2015
Posts: 676
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From: south east kansas
so heres the point where i'm ready to find a new truck, when i push forward or back on the turn signal lever the brake light comes on like it should. so i guess i'm gonna pull the steering wheel and see whats up.
Fleet Mechanic
Joined: Sep 2014
Posts: 1,626
Likes: 78
From: NE Texas
Best I could suggest is to take a look at what moves when you wiggle the lever - if the whole switch moves that is one thing, if the switch is tied down pretty tight and nothing outside of it is moving I would suspect the switch itself. If it were mine I think I would suspect the switch if you have checked all the other connections and grounds.
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