2 wiring questions

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Dec 28, 2003 | 10:53 AM

79 grn on grn

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Joined: Oct 2003

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From: Princeton kentucky

2 wiring questions

First question is: I order an entirely new interior light assembly for my 79' f-150. I also ordered new door switches. Hooked it all up and still doesn't work. When I put the switches in I noticed the switches have three receptacles on the plug end and so do the plug end coming from the truck. However, there are only two wires on the truck end of the plug. This is on both sides, am I missing a wire from both sides or is it suppossed to be like that.

Second question is: On the plug coming from the brake light switch on the pedal the are two wires. One of those wires on my truck has a direct power run straight from the battery, that someone has installed. When I turn on my blinker it flashes normally until I press the brakes then it flashes quicker. If I disconnect the wire my brake lights don't work. It couldn't be the brake light switch because it works when the direct power is hooked up. Could it? This is not a major problem because all my lights work, but this truck had/has a lot rigging on it I am trying to get it straightened out and fixed right. Any help appreciated.

Dec 28, 2003 | 11:23 AM

sparky

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Joined: Jun 1999

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From: Comox Valley, Canada

Well since someone has done some mods to the brakelights.........it is hard to fault find it with the stock wiring diagram

So my best guess would be try a heavy duty flasher unit for the signal lights this may slow them down.
The brake light switch in stock form feeds to the centre of the turn signal switch. Then out to the turn signal/brake light bulb (it is the same bulb and wiring from the turn signal switch to the bulb for both). Both brake lights work when the TS switch is in the centre position, and only one when the switch is to the left or right.....meaning ts to left and only the right brake light works.
So if all the previous owner did was switch the power feed to the brake light switch nothing should have changed.......but I dont know if that is all he did.

Dec 28, 2003 | 03:42 PM

78fordman

Cargo Master

Joined: Oct 2003

Posts: 2,833

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From: Jefferson, Iowa

I have a simular problem, the turn signal switch should have 4 prongs then, one for left turn/brake, one for right turn/brake, brake coming from switch, and the constant power? Because my project truck has a custom wiring job, so i would like to get things straight in my head before it start wiring it up.

Dec 28, 2003 | 05:21 PM

sparky

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Joined: Jun 1999

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From: Comox Valley, Canada

I think these are all of them

Left Front turn signal power out
Right Front turn signal power out
Right Rear Brake/turn power out
Left Rear Brake/turn power out
Turn Signal Power In
Brake Power In
Emergency Flasher Power In

Dec 28, 2003 | 05:26 PM

Torque1st

Posting Legend

Joined: Sep 2001

Posts: 30,255

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Do you have a wiring diagram? If you don't they are available in the service manuals on CD from the online store here.

I have fixed several vehicles just by stripping back all of the add-on wiring back to the factory harness and doing any repairs I had to then.

Dec 29, 2003 | 03:18 PM

neh

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Joined: Dec 2003

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on your first question - check the interior light to make sure you are getting power to the lead, I think the driver side one, by using a test light and grounding to the interior. If you are getting power there but not by grounding to the opposite lead in the socket your problem is the other lead isn't making a good ground. I had the same problem and fixed it by removing the socket and cleaning out the threaded hole and then reinstalling to be sure that I had the screw turned to where it had the best contact.