OK I have a 77 F100 ranger xlt 2wd with a 351M. on the passenger fender just to the rear of the starter solenoid is a thing that looks like a relay of some sort.Has a fuse on it. Its not the horn relay. What is this thing and what does it do?

 

Sounds like something that's been added by a previous owner. I don't know of anything that's "factory" that matches that description.
Post a picture if you can.

 

And also the colors of the wires to the relay

 

Trace the wires and find out what it is connected to. Prolly an add-on but now would be a good time to find out rather than when attempting to put out the fire it caused.

Knowhattamean?

 

Does your truck have dual batteries? If so, there's a dual battery relay in this approx. location that has a wire feeding from it that contains a glass fuse.

Look on the cover of the relay for an ID number, post what it is.

 

Or post a pic of it. That always helps.

 

image upload no compression

 

Bueller, bueller? So anyone know what it is and what wires go to it so I can remove it if possible. Also what's the other one all the way to the right?

 

Dont overthink things. When in doubt disconnect it and see what dont work any more.

 

Yeah last time I did that the ICM sheit the bed. So anyone else know what these things are?

 

That might be a headlight relay. It was a common Delco part back in the days
of 6 volts and generators. The switch would trip the relay sending 6 volts off of the
regulator directly to the seal beams. I could be wrong.
I installed one on our 40 Buick. On idle, the seal beams would dim This kept them
bright at all times.

 

Just an idea- maybe a proto-type Flux Capacitor? It will not actually move you through time, but it does give the very real feeling, of driving a 37 year old pick up....

 

I'd be concerned with the orange fused wire just sitting on your fenderwell. looks like an awesome short. No idea what your mystery part is though. Looks like it's just looped around to itself. if anything, pull the glass fuse on it and see what doesn't work. Shouldn't burn anything up, as that would be no different then it blowing.

 

I chased the wires coming from this thing and it goes into the dash and is connected to nothing. Truck is being rebuilt and I have no idea what the PO has done to this thing. So any help? When I turn the key to right before start that thing clicks like a relay

 

No one here is going to be able to tell you what some custom (now partially removed) piece of equipment was intended for. The only person who can do that is the PO. The crimp terminals and fuse holder (not rated for underhood use by the way) clearly exclude it from anything factory.