need brake relay for my sisters slick

[f100fordguy]

Hey guys, my sisters 66 has this silly 4 wire relay under the master cylinder on the inner fender that went bad and now the brake lights dont work. I cant find anyone who carries them new, do any of you guys have one from a parts truck or know how to bypass it so I dont need it. Thanks
Tim

[Uncle Skip]

???
I thought it had a pressure switch in the brake line. Should only be two wires. One from a 12 v.+ source to the pressure switch and one from the switch to the brake lights.

[bobenhotep]

If it is a bosch 4 pin they are like 6 bucks at the auto parts store. Do you have a picture of this item and the accompanying wiring?

[bruceandersson]

My camper special has this as well. I have not dug into it yet, but think it is some sort of factory trailer wiring.

[banjopicker66]

The only relay I know of in that area - that was factory installed - would be the overdrive relay. It would have nothing to do with the brakes, though.
Even so, that relay is normally mounted on the firewall, between the speedometer cable and the fender, above the parking brake cable. Power to the brake lights is supplied through the turn signal switch.
Can you post a picture?
Does the truck have trailer brakes, as mentioned earlier?

[f100fordguy]

Yes it does have trailer lights. Got a ford part number for it but they said it was nla. Will get pic of it tomorrow when I go to my parents. Its just a small relay with 4 wires going into the top. If I can get rid of it I will. Just trying to figure out what it is cuz my fridges just have the 2 wire on pressure switch. Let me know what bosch number relay is if it will work as replacement.
tim

[Toyz]

Let's start with the basics if you haven't already. With key on do you have power coming to the brake lamp switch at m/c? Probably a red single wire. If it has power, remove both wires and jumper them. If lamps work with turn signal in off position, replace the pressure switch. If they do not work, trace the output wire. If it does in fact feed through the relay rather than having a parallel wire feeding off the switch output wire , clip that wire near the relay, find the same color wire near the bulkhead connector and tie the two together. That will bypass the relay and feed the brake lamp power to the turn signal switch. I would expect the relay to have no effect on the truck brake lamps since it should be a parallel circuit. The relay can be tested by checking the individual wires at the terminals. The terminals should be labeled. Just provide power to the grounded relays main power and load inlet power, then check for power at the load output terminal. If found defective take it to your local auto parts to match up.
Paul

[66camperspecial]

My 66 has one and wondering what it was for.

[bruceandersson]

OK, I dug into the relay mystery. Mine is located on the inner fender beside the rag joint. It has four wires (red, green, green , and black going to a four prong plug, black is insulated the two green are in the middle are male and the red is male. This connects to the opposite plug with black, red and green. The black wire is ground. The red wire from the second harness goes to the brake side of the brake light pressure switch. The green wire plugs into the red wire that normally comes from the brake pressure switch. What this appears to do is just place the relay in line with the brakes lights, I guess to prevent overdrawing the circuit. The wiring harness to the rear was also different from std. right at the back of the cab, the yellow, green and brown wires are split. This was definitely factory. For my truck the second set went to the trailer connector. I did not get a pic of this. There were also a red and white wire in the harness that were cut off at both ends. The white appeared to go to a ground bolt beside the brake res, and I suspect the red would have gone to a hot connection somewhere, or been available for electric trailer brakes. This was totally different from any diagrams I found on the web.

http://i1231.photobucket.com/albums/ee5 ... 110826.jpg

[Toyz]

Yep, that appears to be standard on the Camper Specials. It can run to either a connector at the front of the bed or back to the rear for trailer lamps, or both. The purpose is likely to avoid overloading of the circuit with the additional lamps. If not pulling a trailer or a slide-in with brake lamps, it could be bypassed. Replacement relays are readily available, even a multi- circuit relay could be utilized.
Paul

[bruceandersson]

You can also just bypass the relay by connecting the red wires directly to the pressure switch, leaving the red and green wires from the relay disconnected. That's how mine was connected. I had to stare at it for a while to figure out how it might have been set up before it was disconnected. Check to make sure the pressure switch hasn't failed by jumping between the two red wires coming from the dash.