On my 1969 350 Ford would my Marker Lamp relay switch be the cause of my truck not starting? None of the lights are working either. The only thing that works is the horn.

 

This link should help you find where you are loosing power
https://www.ford-trucks.com/forums/1...w-starter.html

Dont know what a "marker light relay" is but it would not have anything to do not having power to anything but the horn.
Can you post a picture of this marker light relay so we know what you are talking of.

As a guess I am thinking you are talking about the starter relay that we call a solenoid that is bolted to the inner fender well that the battery cable goes to.
But before you get too deep into this pull out a volt meter and lets see what the battery has for power.
Check the battery on the POSTS not the cable clamps. If it dose not have 12.6 volts charge the battery.

Wile the battery charges pull both battery cables and clean the cables and posts.
Follow the cables and clean the other ends and where they bolt to.
One should go to the solenoid in and a cable out to the starter clean both ends of that cable too.

The ground from battery should go to the motor somewhere, clean cable & mount.
You should also have a cable from motor to frame, clean both ends of cable and mounts.
Last should have a 10ga wire from motor, intake bolt or back of head bolt to firewall to ground the cab.

With all that in place you should not have any issues with no power if the fuse links are good at the solenoid.
Dave ----

 

Thank You for your reply, I have attached a photo of what I was referring to.
I put in a new battery & relay switch, and I can get power to the switch here in the photo, but doesn't go beyond. It goes in one side, but doesn't go out the other.

 

I don't know what that relay is for. It looks like it's a horn relay, but I can't make out the p/n# to be sure.

I assume one of those black wires is constant hot connected to the battery. The other black lead is to power whatever load that relay is the switch for. The brown wire is the trigger wire, so where ever that leads back to is what triggers the relay to pass power through to the load. The ground is the case itself when it gets bolted to the body.

 

Probably for the 350 model, which may have come with overhead cab lights. Does yours have the marker lights on the roof?
When you check power, are you checking with the headlamp switch pulled out? Pretty sure that's the only thing in play with this relay. Just the main light switch on the dash.
Since none of your other lights work either, you might check the light switch and it's main connector.
But before that...

When your truck won't start, what EXACTLY is happening? You turn the key to START and what? No click at all? A good click, but the starter is not cranking the engine?
Or does the starter crank, but the engine won't fire up?
When this happened the first time (or is this the only time and all is still dead?) did you get a click and then nothing? No other accessories except the horn? Like no heater fan, no turn signals or brake lights?

Just a few more things to drill down through to help us help you find the main issue. Which might turn out to be multiple issues, when dealing with older rigs like ours.

Good luck.

Paul

 

It does not start, there is no click no nothing. Again, the only thing that will work is the horn, I have gone through the wiring harness; have taken off the battery cables; cleaned off all the grounding cables to the frame & motor, and have changed out all the fuses. There is heat that goes to the hotwire, but nothing else.

I'm getting ready to order a relay switch & see if that works.

Thanks,
Rod

 

Do you have a horn relay on the fender also?
If so, it sounds like either one of the battery cables has failed completely (low on the list, but not impossible and happens a lot to our older trucks) or the fusible link is burned out on the main power wire.
The horn relay gets it's power directly from the starter relay/solenoid connection. Meaning that power is getting from the battery to the relay. But not enough for the other accessories. Leaning me towards the fusible link wire.

Nothing in the fuse panel will keep the engine from cranking, or power from getting to some of the accessories such as headlamps and brake lamps.
It's good to clean them up of course, but there is no fuse for the starter circuit. Only the fusible link keeping power from getting into the cabin.

Which hot wire?

Well, you can do that of course. That will get you a new relay, but of perhaps questionable quality and function. So if you do, make sure to keep the old one. Do not throw it away yet! Wait until you're sure it was the issue.
Can you post up some pictures of your engine compartment around the battery and starter relay and voltage regulator please. I'd like to see where that relay is, and where everything else is. I don't see how that relay will keep power from everything else in the truck. Ford trucks are not usually wired up that way.

Thanks
Good luck.

Paul

 

Part of the reason for the pictures is that in the late-sixties there were a lot of changes to the wiring methods and schemes on our trucks. Especially between the charging system and ignition systems and such.

And do you have the cab lights up top?

Paul

 

I will check it out tomorrow, and take a couple of photo's. To answer a couple of your questions, yes the cab lights are on top. The photo I posted is of the Marker Lamp/ Trailer Relay # C8TB-13A435-A, the hot wire I am referring to, is the black & white one on top of the relay. I have not checked with the headlight switch pulled out yet, but at this point I do not have headlights. Yes the horn relay is on the fender side inside the cab. I am not sure where the fusible link is ? there is a red & yellow wire with inline fuses.

Thank You for your time,

Rod

 

I photo of the horn relay installed but be helpful.............well for me anyway.............That sure looks like my horn relay................May you got 2 of the same relays & 1 is for your lights............
Fuseable links did not appear on F100's until 1972............even though someone installed a yellow one on my truck..................

 

Maybe this thread will be of some help, did you get this fixed? Cab cleareance lights - Ford Truck Enthusiasts Forums

 

I think I remember someone (maybe you) saying that in recent discussions. And I don't remember seeing them in the diagrams. But Ford had been using fusible links on Broncos since at least '67. And cars maybe even before that, so it's surprising to me that they would not have on the trucks as well.
Gotta' dig deeper into that one of these days...

Paul

 



 

In the engine compartment photo, I do not know what the green wire connected to the black is, could that be an inline fuse wire? The fuse below the green wire I can get heat to.

The second photo, both those nuts are hot, and I do not know what these are. It is right next to the marker light/relay switch.

Any information would be great.

Rod

 

I’ll take a closer look in a bit. But in the second picture, that small metal canister with the black top and the studs with nuts, is a circuit breaker.
Most of them are self-resetting once the excess load is removed. But some are not.
And sometimes they can actually fail too, which breaks the circuit flow.
I’m not sure why it should get hot though, unless there’s too much current flowing through it.