I just purchased a new toy that hasn't seen life in over 20 years. So I have rebuilt the carb and cleaned out the fuel tank. Now it is time for electrical. There was no ignition switch and a bunch of spliced wires with only tape holding them together. I cleaned a bunch of it out and trying to sort through it now.













I want to sort out ignition first, I bought a new switch that doesn't label what the connection points are. I got confused with a couple different wiring diagrams that I was looking at because they conflicted each other. Would I be correct with connecting ;Black green to accessory ,red blue to start, pink to run and yellow to bat? Also does anyone have a picture or diagram of the back of the switch on what spade is what? The truck sits on a 79 frame with the 400M so my next question do I need to rerun a different wire to the solenoid for the electronic ignition instead of the pink resister wire?

 

Nice Truck! What year? Not knowing, seeing, all that has been messed with, I'll ask a couple questions. Your new ign switch, correct one for the truck, not a universal replacement?

Pink resistor wire joins, splices with, the wire from the I terminal of the starter solenoid and the wire that goes to the original coil. The splice is in the harness, its taped up. When converting my truck, 66,F-250, 240 engine pts and cond to DUII, I left the pink wire in place and used it.

Red with blue tracer to solenoid S term (at ign switch and should match at solenoid S term)
Red with green tracer is the third wire in the splice mentioned above and fed the original coil. It goes to to the coil on your 400M (at coil on engine).
Black with green tracer to acc term (at ign switch),
Also on ACC term on my truck is the feed wire to the W Wiper switch, that wire is a pigtail, red with grey plastic connector and the other part of grey plastic connector orange with white tracer, it went to the W W switch.

Assuming you have the 400m Dizzy (distributor) there is a needed wire to power the box on your fender well or wherever they put it. There is a 2 wire connector on the box with a red wire and white wire. The red wire powers the box. In my conversion ( and my unmolested wiring) the pink wire connected to a pig tail off the ign term and I made a 1 into 2 connector and added a RED wire to go to the box.

The purpose off the white wire is to retard the timing as you are cranking the engine, If needed. I don't have that wire hooked up, although after setting my timing with a vacuum gauge, I have slight kick back when starting. When I hook up the white wire, I'll probably hook it to the S term of the starter solenoid.

Hope this helps you, tell us how you make out.

 

That's a damn cool Merc. Hope ya get it going.

 

Thanks guys! IICAP the truck is a 64 and it is a factory type replacement switch but it doesn't say what terminal is what and I didn't buy the $55 pigtail. When I bought the truck it didn't have any switch just a bunch of wires hanging. Your explanation difinetly helps though. The PO also added the 79 tilt column which I have done before on my 69, so should be able to figure the wiring fiasco on that out.

 

This looks like a disaster ready to happen as well.





Should this be ok if I just fix up with some good shrink wrap butt connectors? Are those spliced in fuseable links necessary?

 

This is the back of the ignition switch I was hoping that someone might know what spade is what.


The one where my thumb is not used by my understanding and the centre post is the accessory.
Top left?
Top right?
Bottom? (Think this one is yellow for bat)

 

Fuseable links for safety. Depends on what they are protecting. Heat shrink connectors always a good choice. Trim wires back enough to get all strands in a crimp

I'm not in position to take ignition switch out of my truck to look. Maybe someone reading thread has a truck with dash out or ign switch hanging and the can tell us

If you have DVOM (digital volt ohm meter). You could try to check the terms and label yourself, I THINK, just have to try. I'm guessing 4 maybe 5 spades. I would try anyway. You need make diagram of spades and note what you find as tested.

This whole thing might be a waste of time

1- Key off, hopefully no contact between any spades.
2- Key on acc, contact between 2 spades would be batt spade and acc spade, note
3- Key on run/ign, contact between 3 spades would be batt, ign, acc. The third spade
just added to other two in #2 test will be "ign", note
4- Key in start position, contact with last spade not used yet would be "sta"or "start"
5- Bear with me, thinking all this as we go along here. When testing #2, would either of the two spades be heavier/wider than the other. We are looking for the spade which is the "batt", heavier one would be it. If no heavier spade, I'm lost here. I cannot come up with a way to determine which of the 2 are batt and acc, but it must matter.

 

The big stud is the accessory terminal. And you say there is no letters of marks identifying the spades.

 

Nice Mercury !

I did a quick search, this post explains the ignition switch terminal layout:

https://www.ford-trucks.com/forums/1...on-switch.html


I took a pic of a spare ignition switch and wiring from a '65 or '66:




I used my multi-meter to check the connections, this is how it relates to the wiring colours that IICAP mentioned:

 

DanK, thanks for posting that info. Thought someone out there knew it.

 

Thanks guys, that remedies that.