I just bought this 1971 forn 150 the brake lights were working. now they wont work. all the fuses are good, all the bulbs are good. The brake light switch is working, so where do i go next. If you can help I can be found on here or on aol at unclegmacd(No Email Addresses In Posts!)

 

Well if all those are good it must be a bad wire between the switch and the lights or a bad ground

 

I'm not sure if they were the same in '71, but on my '79 I had no brake lights for years just because of a bad connection at the fuse block and a bad fuse. This would be one place to check.

 

Take a test light to it, making sure that the test light is properly grounded, if that doesn't test good then check your ground. But if the parking lights work, then it is not the ground. Does your hazard lights work? Check for continuity between ground and the side of the brake switch that doesn't go to the fuse panel if you don't have cont. there, change and wiggle the light bulbs, clean the contacts. This should get it.

Chris

 

If the 71 is the same setup as the 73-79 the problem could be the turn signal switch as the brake light circuit is routed thru the switch.
Also could be a corroded ground, but if I remember right there is a separate ground for each light assembly LH & RH, and the same ground is used for the turn signals and the tail lights on that side of the truck.
Check for 12 volts at the brake lightbulb sockets. Once again if I remember right, there should be a connector close to the rear of the truck that brings tail light, brake light, signal light and reverse light power to the rear light harness. It may be corroded or have a broken wire. Just start tracing the wires back til you find a broken wire, bad/corroded connector.
When you say the switch is working do you mean there is 12 volts in and out? Just because a switch clicks doesn't always mean it works
Good luck and let us know the results.

Sparky

>I just bought this 1971 forn
>150 the brake lights
>were working. now they wont
>work. all the fuses are
>good, all the bulbs are
>good. The brake light switch
>is working, so where do
>i go next. If
>you can help I can
>be found on here or
>on aol at unclegmacd(No Email Addresses In Posts!)

 

Crawl under the rear with a light tester and remove what ever jerry-rigged trailer connection the last owner did to it and start over at a point where the wires haven't been touched so you know what you're working with.

You've certainly got a rare truck there. I wasn't aware Ford even made an F150 in 1971.

Trail Rider

 

TrailRider is right. I had light problems too on my '76 so I decided to pull out (carefully) all of the excess and unused wire. I pulled out an old, old alarm system (seriously, it had a motor driven siren), a non-working (permenantly) after market air conditioner, a non-working after market cruse control (this thing had hall effect sensor on the drive shaft!), and at least 3 three different hack jobs of hooking up trailer lights. After pulling out about 2 miles of wire and making sure everything is sealed, my light problems have just gone away. I even drove it in the torrential rains we've had today to be sure.

Matt Miller

 

Have stand behind the truck, apply brakes and wiggle turn signal switch. If brake lights come on it is the turn signal switch(seems to be a common problem). Also check to see if the tail/brake light bulbs are in properly, I have seen people put them in backwards and push hard enough to actually seat the bulbs. But if you have not replaced them and they were working then this can not be the problem.
good luck.

HeavyMetal (Rod)
1977 F100 429CJ bored 30 over, Heads milled 30, edelbrock performer cam, intake, lifters, valve springs, Flat top forged pistons, polished and ported, Holley 750 Legacy, Hooker Super Comp. headers with dual Hooker Comp. exhaust and Hooker dual resonators, B&M C-6 racing tranny, with a TCI Breakaway 2600 flash stall converter, 9" rear with 2-72 gears.

 

Myself would start at fuse box, power in first to box , then fuse itself, then take two screws out of fuse box turn around then check the back side, then to brake switch, in and out sides of it. Then would check and see if someone has had the tranny out latley and see if the layed across the wiring harness and has cut it in half. And if you have it that far back its bulbs or ground, (dietric grease in them socket and connect help them to be trouble free for years) One other thing that was mention about trailer lights. For me I got the connect from same truck at junk yard , Cut 5" or 6" from connect and splice them back to togeather with trailer pig tail, now just plug in with needed and remove in less than a minute, just my thoughts

GWB

 

definitely check the fuse block, on my 70 I found where an interior leak had corroded one contact, I repaired it and when I turned the truck on and then off it still ran even with the key out of the ignition. turns out the previous owner had hot wired the tail lights. they would come on but wouldn't react to the brake pedal. Also the truck had been changed from 3 on the tree to 3 on the floor and my back-up lights didn't work. I located the female plug under the hood where the back up switch used to be, ran wire into my cab using the same path as the speedomoter cable to the tranny and upinto the shifter boot, made sure the wires cleared all the linkage, and secured the original female plug with a new switch to the floor so that when I shifted into reverse - oila! works great.

 

Hey Rob, You recon he got it fixed in the last 12 months. He posted that a year ago.
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John

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[link:www.ford-trucks.com/users/jowilker|My Club FTE Page] Member since 01 01

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Hey John, at least they're reading the old posts!

Barry