PLEASE HELP!!!
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Junior User
Joined: Jan 2001
Posts: 67
Likes: 0
PLEASE HELP!!!
My truck is an electrical nightmare. Here's the story. When light switch is OFF everything works fine except when I press the brakes my front turn signal lights and roof marker lights light up with the brake lights. When my light switch is ON my brake lights are stuck on, left rear turn signal works, right rear doesn't, roof marker lights and front turn signal lamps get brighter when brake is applied. And sometimes when light switch is on everything works fine BUT I have no rear running lights (tail lites). AHHHHHHHHHH!!!!!!!! I've been pulled over 3 times and next time I get impounded. HELP ME PLEASE!!!
Thanks
'81 Ford F150 4x4
300 I-6
NP435/208 Case
Thanks
'81 Ford F150 4x4
300 I-6
NP435/208 Case
Elder User
Joined: Mar 2001
Posts: 898
Likes: 0
From: SF Bay area
PLEASE HELP!!!
Hi, you should start by checking ALL bulbs (sounds like they work), but maybe you have a wrong bulb in a socket so the current will pass thru and lite all bulbs if there is a single filament bulb in a double filament socket. Then check fuses as a matter of course. trace your wiring as ther may have been chafing and taillite and stoplites are "connected". after all that, verify the headlite switch is ok. good luck...
Wayne
Wayne
Cargo Master
Joined: Jul 1999
Posts: 2,484
Likes: 7
From: New Egypt, New Jersey
PLEASE HELP!!!
Hi, My brother had the same problem on his '77. It turned out to be the wires touching together like Wayne mentioned. The symptoms were identical to yours. The problem was in the rear of the truck. There was a wire harness put there for a trailer at one time (which we didn't know existed). The ends were only taped together. It drove us nuts 'till we finally found it! Good luck!
Kenny
Kenny
New User
Joined: Apr 2001
Posts: 4
Likes: 0
PLEASE HELP!!!
I would also look for bad grounds in any socket with two bulbs or with a dual filament bulb. In either case, when one filament receivs poower, it will go across the floating ground to the other filament, through it, and to any filament in that filaments circuit that does have a ground.
Thus if a tail light assembly is floating, the heavy brake light bulb will ground through the tail lights or any other lighter filaments in that circuit. The brake light filament will not glow, but the lighter filaments will.
If you have any doubt about any ground, take a long wire, connect it to battery ground, and then use it to ground each questionable socket, being sure to remove any rust on the socket first (rust is an excellent insulator at 12 volts!). If things get better with the test ground connected to any given socket, start the process of cleaning that socket, whate ever it grounds to, etc. until the socket gets its normal ground back: then move on to the next socket.
Thus if a tail light assembly is floating, the heavy brake light bulb will ground through the tail lights or any other lighter filaments in that circuit. The brake light filament will not glow, but the lighter filaments will.
If you have any doubt about any ground, take a long wire, connect it to battery ground, and then use it to ground each questionable socket, being sure to remove any rust on the socket first (rust is an excellent insulator at 12 volts!). If things get better with the test ground connected to any given socket, start the process of cleaning that socket, whate ever it grounds to, etc. until the socket gets its normal ground back: then move on to the next socket.
Senior User
Joined: Apr 2000
Posts: 396
Likes: 0
PLEASE HELP!!!
Even if there is a trailer plug wired in (instead of cut off and taped) check that wiring. Good Luck!
88 F-150 4X4 XLT Lariat w/5.0 EFI 5 spd (DAILY DRIVER)
86 Ranger 2WD w/2.3L EFI 5 spd to be 351W 4bbl C4 (NEW TOY- DETAILS WHEN FINISHED)
85 Old Cutlass Supreme 350/TH350 Holley 4160,Edelbrock Performer intake, el-cheapo headers, High Energy Cam 270H series cam, 15.588 best 1/4 mile with original 10 bolt 2.41 gears (OLD TOY)
88 F-150 4X4 XLT Lariat w/5.0 EFI 5 spd (DAILY DRIVER)
86 Ranger 2WD w/2.3L EFI 5 spd to be 351W 4bbl C4 (NEW TOY- DETAILS WHEN FINISHED)
85 Old Cutlass Supreme 350/TH350 Holley 4160,Edelbrock Performer intake, el-cheapo headers, High Energy Cam 270H series cam, 15.588 best 1/4 mile with original 10 bolt 2.41 gears (OLD TOY)
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Senior User
Joined: May 2001
Posts: 244
Likes: 0
PLEASE HELP!!!
Well, I'm just going to have to agree with all these other fine folks, but especially the ones that say check the grounds. I've had my run ins with crazy stuff. I've had my license plate lights blinking with the turns signal, I've had my hazzard lights wig-wag when the lights are on, I've had one brake light get brighter, and the other one go out, once again, only when the lights are on! Lots of trouble is caused when circuits try to share. If all else fails, buy a dozen toggle switches, rip out all previous wiring and make your own.
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Brett Foote
Senior User
Joined: Nov 2000
Posts: 231
Likes: 2
PLEASE HELP!!!
You didn't mention the year of your truck so I don't know if this will help. A friend of mine owns a 4x4 shop and while visiting one day he asked if I have ever seen this particular problem(S) before. The truck would do crazy things when you would energize the ignition to run and then try to use different electrical devices. The windshield wiper switch when depressed would start the truck, pull on the lights and the wiers would go and ETC. Well what he found was at the junction block at the firewall (outside) most of the wires, due to under hood engne heat I guess, had their insulation recede back from the junction block and allowed some wires to touch one another causing the erratic electrical problems. He had to dis-assemble the harness and shrink wrap each individual wire to aleviate the problem. I hope this helps.
Todd
BB79RANCH
Todd
BB79RANCH
Freshman User
Joined: Jun 2001
Posts: 31
Likes: 0
PLEASE HELP!!!
I had a similar problem on a 76 3/4 ton before. With the lights off and brake pedal applied headlights,park lights, interior lights and probably some other stuff happened. Any way I had it at the local parts store and the mechanic there told me it was a bad diode in the alternater and I needed to replace it. YEAH RIGHT...... I thought, the alternater. He said if that wasn't the problem he would buy the alternater for me. Anyway I changed the alternater and it instantly fixed the problem. Might not fix your problem but it might not hurt to try.
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