My son just bought a 1984 F-150 351 Windsor four-wheel drive. He replaced the alternator because he thought it was bad, but he found this relay on the firewall, and though I found a picture of it on a bronco, his schematics says it's an engine control module for his truck. That can't be right.

I work in auto parts over 18 years ago, for 10 years. Now we used books back then to look things up, but when that would bring up the wrong part, we would go to the pictures and could almost always find what we were looking for even though it's supposedly wasn't supposed to fit. I looked through every picture of a Ford relay on the internet that I could find. I cannot find anything that looks exactly like this, except for the one that I saw on this website that fit an 84 bronco 351.

Now his mechanic but he's only 20 years old and he works in a Chevy dealership with new cars.

Help this mama help her boy out.



This is his actual relay with the prongs exposed

This is a side view of his actual relay

This is the picture from the bronco from this website.

 

On my 86 302EFI, that is the fuel pump relay. From what I understand, that relay is used in a few places. Here's a photo of it in my 86'.

Does his truck have an electric fuel pump in the gas tank.

You can find lots of info under the "documentation" link, then Electrical, then under EVTM in this forum/link. https://www.garysgaragemahal.com/

One of the experts will chime in soon, they know much more than I do.

 

See post #6 here, trailer brake relay. I searched google for something like, 1984 Ford F150 351 relays on the firewall and found a link to that.

https://www.ford-trucks.com/forums/1...e-booster.html

 

That doesn't look the same

 

Welcome to FTE

At first I was going to say it looks like the relay for the horn / speed control if the truck has speed control (cruise control) but then you say fire wall?
So I was thinking it was a relay for trailer lights, and may still be for that, then see a picture where on the firewall it is / was.
Thing is they dont look like factory wires going to it or are they? Where do they run to? Being you have it pulled what stopped working?
Being it has wires going to it I would follow them and see where they go and can then figure out what it is and for.
Sorry got nothing else
Dave ----

 

After a nap, I am an old fart, I seen I forgot to hit send on the above post and when I went to see how it looked see that Max posted something.
I also get thinking that picture was not of your truck but from the Bronco site so what I said about the wires is not true for your truck

Now Max linked a post and they said "trailer brake controller"? I have pulled many a trailer with just as many cars & trucks and none ever had a "trailer brake controller" that looked like that?
They were always inside where the driver could reach it to apply the trailer brakes manually. Old school ones may of had a variable resister under the hood to adjust the trailer brakes for when loaded and un-loaded like a car trailer might be, so they would not lock up when empty. New controllers you can adjust right on the controller and adjust on the fly.

Now like I posted if the truck came with trailer tow package it may of had a trailer light relay as part of the package. It could also been used for a slide in camper as it had lights being it covered the taillights.
Fords are known to trip the breaker in the head light switch when they get old and then put more load on it with extra lights from a trailer or slide in camper and they trip even faster, I know this for a fact!

I am going with trailer light relay but is you have a picture of the wires connected to it that may help us tell what it was.
Dave ----

 

He may have a trailer tow package on it. This picture calls it a trailer lights relay. If it has a darkbrown wire going to it, it's for the trailer marker lights.

 

Did you click on that link, see post #6. Which is what Dave F is showing. Post #7 show's a truck with it.

In my first post above is a link to where Dave got his info/diagram from.

 

I hate to break it to you like this, but you were an old fart before your nap, too. This particular nap did not change your old fart status.