"Brain" box question
 

Not sure the exact name of it, but my question is concerning the aluminum box mounted to the inner fender near the firewall. The wire harness in my 77 (302 3-speed) was cut up pretty bad and I found an unmolested 75 (302 automatic w/ AC)truck to use parts from. After changing complete harnesses, I had no spark. Anyway I exchanged the box from the 75 and truck ran fine. There are different colors on the back. One was green and one was blue. Do they differ by years of wire harness, engine size, or transmission, or AC? Is there a chart as to which one I should have? What exactly does it control. I got the problem fixed, just not sure why.
Thanks,
Shane

That is your ignition module(box). I don't think there is a difference b/w the two. As long as it runs your are set to go.

429 fordman beat me to it. I currently have a 77 box in my 76, no problems.

That is the Duraspark ignition module.

1974-1975 = Duraspark-I
1976-1983-up = Duraspark-II
1980-up (Certain California Engines) Duraspark-III


They are drasticly different between, 1974-1975 and 1976-1977. And the wiring harness is also drasticly different. Why it didn't run with the old Duraspark-II box.

You changed from a Duraspark-II system to a Duraspark-I system.

I'd find another donor vehicle with the right Duraspark-II wiring harness, and Module.

This is because the Duraspark-II modules are cheaper and more easily accessible, and still avaliable to buy from Ford.

Ford no longer makes either one of the DS-I modules, and not sure of the avaliability of them aftermarket either.

That's because both the 1976 and 1977 use a Duraspark-II module. Blue Grommet.

The 1975 uses a Duraspark-I, Green Grommet.

The systems are not compatible with each other.

Why the Blue Grommet DS-II module didn't work, after he changed his wiring to the 1975. He now has to use the 1975 DS-I module.

Good to know. I already exchanged the entire harness from the 75 and the module. I didn't find many differences. There is no seat belt buzzer, ignition switch plug was different, engine feed came from the other side, and the brake proportioning valve switch was in a different place. With the 75 it came from the firewall harness, with the 77 it came from the tail light wiring harness. Truck runs ok but haven't tested it on the road yet. I hope there aren't any other big differences. I am not looking to switching the wire harness again if I don't have to.
Thanks for the info. Do they go bad often? Should I keep an eye out for an extra Duraspark I to have on hand?
Shane

It would be a good Idea.

They fail just about as often as the DS-II module. A spare Is always a wise decision.

I keep a spare DS-II module in my 1981 for example. But I travel a lot in the middle of nowhere too.

Just make sure you find a DS-I Green Grommet for a 1975. and Have It tested to make sure it's still good.

As for other differences, the major ones are the DS-I module and wiring, and the Instrument cluster wiring and printed circut. When you buy parts from now on, It might be easier to call it a 1975 for certain items, a 1977 for others. ;) Not unlike the old Johnny Cash Song. ;)

Love that song. Have to record that one onto cassete so I can play it in my truck. The song that really reminds me of it is Drive by Alan Jackson. My first truck was just like this one. That song probably got me thinking about buying an old Ford like this. If it's Alan's fault, do you think he should chip in on the restoration?