HELP!!

[1971fordcustom]

Well on my 71 F-350 My Cablights went out! Well no power to them! I Traced the wired to a Relay or something, It's Behind the glovebox on the right side,Its bolted to the side panel, It has 3 wires coming out of it!
What is that thing? Cab lights work when I took a jumper wire from a hot wire to the cablight wire and bypassed that part.

[Racer Z]

The silver box thing... Hmm... I'm pretty sure my F250 C/S has two. And, yes, the F350 shares this with the F250 C/S. One is a relay and the other is a circuit breaker. If I remember correctly from looking at the wiring schematic, it services the roof marker lights and the side markers on the front fenders.

Replace the box that you jumped. A circuit breaker has only two wires and a relay will have four or five. You can get these at any auto parts store. Take the old one with you.

[1971fordcustom]

The silver box thing... Hmm... I'm pretty sure my F250 C/S has two. And, yes, the F350 shares this with the F250 C/S. One is a relay and the other is a circuit breaker. If I remember correctly from looking at the wiring schematic, it services the roof marker lights and the side markers on the front fenders.

Replace the box that you jumped. A circuit breaker has only two wires and a relay will have four or five. You can get these at any auto parts store. Take the old one with you.

I did take it to the auto part store! no LUCK! The place I took it to know there stuff to, but no luck

It has a lil silver but most of it is black. C8TB-13A435-A is the#

[Racer Z]

That part number came up as a relay. I did a quick search at LMC and did not find it.
If it was my truck, I would buy a Bosch relay and wire it in myself using that connector plug.

[Thunderfoot]

That is a Relay for the Marker Lights it should have a circuit breaker right there next to it, be sure you have power on both sides of the circuit breaker just to be sure it is not the problem. The power comes from the battery to the circuit breaker then goes to the Relay.
The Relay has 3 wires on it: one from the circuit breaker, one to the Marker Lights, and one from the light switch to turn the relay on, see this diagram here http://www.fordification.com/tech/wirin ... arkers.jpg same relay setup is used for Camper Specials for the marker lights and such.
The relay is nothing special it is just a 12V relay, you can use any (normally open) 12V relay for this, like this one from NAPA will work http://www.napaonline.com/Search/Detail ... 0252376254

[knightfire83]

If he's bypassing the marker light relay and then has cab lights, that means that he is back feeding the electrical system from that point which has a direct 12v source from the battery. Chances are the relay and breaker are fine. Problem is that there is no power feeding the light circuit from the headlight switch.

I suspect a bad headlight switch or loose connections at the switch. Check the instrument light fuse yet?

[Thunderfoot]

If he's bypassing the marker light relay and then has cab lights, that means that he is back feeding the electrical system from that point which has a direct 12v source from the battery. Chances are the relay and breaker are fine. Problem is that there is no power feeding the light circuit from the headlight switch.

I suspect a bad headlight switch or loose connections at the switch. Check the instrument light fuse yet?

1971fordcustom said that he jumped from a 12V source to the marker light wire, that would jumper out the whole circuit including the circuit breaker and relay components so it is hard to tell if the problem is the circuit breaker, the relay, or the relay control signal to the relay... only way to tell is checking it with a test light or voltage meter to find out what has power and what doesn't...

Also, the "instrument light fuse" has no bearing on the situation as it is not in the circuit, this fuse is strictly for the instrument lights. The power for the instrument lights comes from the light switch rheostat and then goes through the instrument light fuse and then to the instrument lights, as you dim the lights less voltage goes through the fuse...

The relay control signal for the cab marker lights is controlled from the same wire for the tail lights on the rest of the truck, so if those lights work then the problem is not the light switch. It could be the wire somewhere in-between is broken or come unplugged, but for it to be the light switch the tail lights also wouldn't be working.

[1971fordcustom]

If he's bypassing the marker light relay and then has cab lights, that means that he is back feeding the electrical system from that point which has a direct 12v source from the battery. Chances are the relay and breaker are fine. Problem is that there is no power feeding the light circuit from the headlight switch.

I suspect a bad headlight switch or loose connections at the switch. Check the instrument light fuse yet?

1971fordcustom said that he jumped from a 12V source to the marker light wire, that would jumper out the whole circuit including the circuit breaker and relay components so it is hard to tell if the problem is the circuit breaker, the relay, or the relay control signal to the relay... only way to tell is checking it with a test light or voltage meter to find out what has power and what doesn't...

Also, the "instrument light fuse" has no bearing on the situation as it is not in the circuit, this fuse is strictly for the instrument lights. The power for the instrument lights comes from the light switch rheostat and then goes through the instrument light fuse and then to the instrument lights, as you dim the lights less voltage goes through the fuse...

The relay control signal for the cab marker lights is controlled from the same wire for the tail lights on the rest of the truck, so if those lights work then the problem is not the light switch. It could be the wire somewhere in-between is broken or come unplugged, but for it to be the light switch the tail lights also wouldn't be working.

New relay but still no luck! Crcuit breaker is good, All my other lights work just fine! No broke wires for the cab lights! On the new Relay there is 3 markings, H-b-S I've tryed every wire every way but no luck! Only way they work if I put a hot wire on cablight wire! Unless that relay just wont work!

[Racer Z]

New relay but still no luck! Crcuit breaker is good, All my other lights work just fine! No broke wires for the cab lights! On the new Relay there is 3 markings, H-b-S I've tryed every wire every way but no luck! Only way they work if I put a hot wire on cablight wire! Unless that relay just wont work!

I think this question has been asked, but I don't remember it being answered, so I will ask it again.

Is power coming from the switch to the circuit breaker?
Is power going from the circuit breaker to the relay?

Lets get that answered before we move on to anything else.

[1971fordcustom]

New relay but still no luck! Crcuit breaker is good, All my other lights work just fine! No broke wires for the cab lights! On the new Relay there is 3 markings, H-b-S I've tryed every wire every way but no luck! Only way they work if I put a hot wire on cablight wire! Unless that relay just wont work!

I think this question has been asked, but I don't remember it being answered, so I will ask it again.

Is power coming from the switch to the circuit breaker?
Is power going from the circuit breaker to the relay?

Lets get that answered before we move on to anything else.

YES!!!!!

[Racer Z]

New relay but still no luck! Crcuit breaker is good, All my other lights work just fine! No broke wires for the cab lights! On the new Relay there is 3 markings, H-b-S I've tryed every wire every way but no luck! Only way they work if I put a hot wire on cablight wire! Unless that relay just wont work!

I think this question has been asked, but I don't remember it being answered, so I will ask it again.

Is power coming from the switch to the circuit breaker?
Is power going from the circuit breaker to the relay?

Lets get that answered before we move on to anything else.

YES!!!!!

Good.

All relays need four connections. Power in, power out, switch power and switch ground. Since I only see three connectors, the ground MUST be through the body. That means it will never work if it does not have a clean connection through the mounting screw. I see two solid color wires and one with a trace (stripe). Traces, in this case are usually switched wires. My guess is that this comes from the light switch. The other two won't matter, one in from the battery and one out the the lights.

I'm looking at the schematic that was provided in an earlier link. I will tell you what Ford has to say about it.

Black w/white trace: (256) POWER IN from circuit breaker. The circuit breaker gets it's power from the starter solenoid.
Black: (207 & 207A) OUT to lamps.

Brown: (285) from switch.
Ground: () through the metal relay case.

A test light is your friend. You should be able to hear and feel the relay pull down if you provide 12 volts to the brown wire and a ground to the case.

A dirty ground will ALWAYS cause problems that are hard to diagnose.

PS. It's a good thing I looked at the schematic cause my guess was wrong.

[1971fordcustom]

I just went back out there to see maybe I was doing somthing wrong! NOTE No key is on the headlight switch is off!, I put the new relay on! the CABLIGHTS light up! I trun the headlights on the fliping cablights so out! WTF Its all stock wireing under the dash!

[1971fordcustom]

All relays need four connections. Power in, power out, switch power and switch ground. Since I only see three connectors, the ground MUST be through the body. That means it will never work if it does not have a clean connection through the mounting screw. I see two solid color wires and one with a trace (stripe). Traces, in this case are usually switched wires. My guess is that this comes from the light switch. The other two won't matter, one in from the battery and one out the the lights.

I'm looking at the schematic that was provided in an earlier link. I will tell you what Ford has to say about it.

Black w/white trace: (256) POWER IN from circuit breaker. The circuit breaker gets it's power from the starter solenoid.
Black: (207 & 207A) OUT to lamps.

Brown: (285) from switch.
Ground: () through the metal relay case.

A test light is your friend. You should be able to hear and feel the relay pull down if you provide 12 volts to the brown wire and a ground to the case.

A dirty ground will ALWAYS cause problems that are hard to diagnose.

PS. It's a good thing I looked at the schematic cause my guess was wrong.[/quote]

I've been useing a test light! And every thing was grounded

The only marker lights I have is the cablights

[Racer Z]

All relays need four connections. Power in, power out, switch power and switch ground. Since I only see three connectors, the ground MUST be through the body. That means it will never work if it does not have a clean connection through the mounting screw. I see two solid color wires and one with a trace (stripe). Traces, in this case are usually switched wires. My guess is that this comes from the light switch. The other two won't matter, one in from the battery and one out the the lights.

I'm looking at the schematic that was provided in an earlier link. I will tell you what Ford has to say about it.

Black w/white trace: (256) POWER IN from circuit breaker. The circuit breaker gets it's power from the starter solenoid.
Black: (207 & 207A) OUT to lamps.

Brown: (285) from switch.
Ground: () through the metal relay case.

A test light is your friend. You should be able to hear and feel the relay pull down if you provide 12 volts to the brown wire and a ground to the case.

A dirty ground will ALWAYS cause problems that are hard to diagnose.

PS. It's a good thing I looked at the schematic cause my guess was wrong.

I've been useing a test light! And every thing was grounded

The only marker lights I have is the cablights

I'm thinking you blew a fuse for the regular running lamps.

[1971fordcustom]

All relays need four connections. Power in, power out, switch power and switch ground. Since I only see three connectors, the ground MUST be through the body. That means it will never work if it does not have a clean connection through the mounting screw. I see two solid color wires and one with a trace (stripe). Traces, in this case are usually switched wires. My guess is that this comes from the light switch. The other two won't matter, one in from the battery and one out the the lights.

I'm looking at the schematic that was provided in an earlier link. I will tell you what Ford has to say about it.

Black w/white trace: (256) POWER IN from circuit breaker. The circuit breaker gets it's power from the starter solenoid.
Black: (207 & 207A) OUT to lamps.

Brown: (285) from switch.
Ground: () through the metal relay case.

A test light is your friend. You should be able to hear and feel the relay pull down if you provide 12 volts to the brown wire and a ground to the case.

A dirty ground will ALWAYS cause problems that are hard to diagnose.

PS. It's a good thing I looked at the schematic cause my guess was wrong.

I've been useing a test light! And every thing was grounded

The only marker lights I have is the cablights

I'm thinking you blew a fuse for the regular running lamps.

Thats what I was thinking, But I just went out there, All my fuses are good. Found out somthing else! when my cablights went on my parking lights turns on also! tryed a wire a diff way the the parking lights and the taillights came on! Im going to see if I can find a old relayfrom a 250 or 350 truck and see what it does. I like to do wireing when I start from nothing, But trying to work on stuff thats been wired by somone else or whatever, GRRR