Re Wiring a S1 4.2 FHC

Hi does anyone have a pictorial of a rewire for a 4.2 FHC S1 all of the diagrams do not make a lot of sense to me and the u-tubes and not much good either.


Sorry, no photos, but it’s not that tough. First thing is to deal with the diagrams and get them to make sense. It’s worth the effort, and there’s nothing as good as the diagrams to get the right wire on the right connector. (However, there are inevitably some errors in there that have to be figured out by you – e.g. the backup light wiring in the dash)

One tip though, hoping that old wiring is still in place, do not remove any plugs or connections; rather cut the wires leaving the plug and color-coded stub in place. Makes it much easier to do most of it.


I recently put in a new bonnet harness in my 1967 FHC (using the helpful tips from Jerry) and it was slightly different than earlier 4.2 S1s. The 3AW was the most significant difference as my car is at the end of the S1 production, but there others including the tach wires. SNG does not take into account all of the changes at the end of the S1s, but I found that Rhode Island Wiring and Autosparks do ( and I ordered my harness through Rhode Island Wiring because they include a very helpful schematic that provides good info on all the connections. It was a little more expensive, but I found it worth it.


I’ve re-harnessed a couple of cars. For me the biggest headache wasn’t getting things connected (I served my time as an electrician), but rather figuring out where the harnesses route through, and which grommets went where.

If the harness is still in the car, then take a lot of pictures, then take a video as you pull it out, and explain where it passes through, and over, and under. Next time I do this I am going to glue a go-pro to my forehead!

Sage advice, Andrew. Also, I believe that the CoolCat colored wiring diagrams are the finest available.


I rewired my 70 2+2 using looms sourced from SNG. I had a wiring diagram for my car that I had enlarged and laminated. I took a lot of pictures before I removed any old wires and as I removed wires. Since I have no electrical trade experience I made note of where everything was connected, what switch, what gauge, what connection. I also tagged each wire, both ends, as to what it was connected to at either end or if it was connected to a splice.
The new loom I tagged each end the same way and made sure I knew where each wire started and ended.
I used the wiring diagram to mark the colors and the looms I bought from SNG matched the colors noted on the wiring diagram exactly.
I did not cut the ends of the old wire from the loom but ‘pulled’ everything out.
I took my time in rewiring and everything went well, no smoke and it all works.
Good luck.

Hi any chance of a copy of the helpful schematic?

Do you have any of the pics you took in digital form that you could send to me?

Some pictures are posted in the ‘Photo Album’ section on the old site.
Since your car is (I think) a 1967 I am not sure how much will be the same but it will give you an idea. My car has a A/C and a ballast ignition system so I don’t think my wiring diagram will be helpful. I mentioned it indicate using a good diagram was necessary for success in my opinion.

Good luck with your project.

Regards, Joel.

I have some photos and diagrams but they may not be right for your car. What is your car ID number?

As mentioned before I have several diagrams, happy to share but as John says, none may be 100% accurate for your car. Do what is obvious and if you bump up against something that isn’t perfectly clear then ask here, someone will likely have an answer. If not we’ll usually try to figure it out with you.

Hi there, I have watched some of your u-tubes but need a pause button on pic but sound to continue, my E number is 1E34153 it is up on there will be quite a few differences between cars but I just need to know that I am in the right ball park I am not looking to nit pick on exact detail at this stage, Thanks for any help. Aidan