Quote:
Originally Posted by psimet
..and that one shows the opposite connection on the ammeter.
Kind of like this one in slide 26...
https://www.mafca.com/downloads/Semi...ex%20Janke.pdf
Also shows the Y/BL to the "Charge" side of the ammeter but calls out that the posts are swapped and it's actually the "discharge" side of the gauge as some reproduction units will swap the post sides making them the opposite of the front of the gauge.
The one you just posted shows the opposite with respect to an original gauge that would have the discharge terminal on the "driver's side".
I understand this is DC and a lot of it is just nuances but the wiring diagrams from multiple sources all seem to have variances. The ones that seem like they are the Ford ones don't even list which side of the gauge is which as an example. |
I recently rewired the ignition portion of my 31 coupe. I also was confused by the many different diagrams for the various years of Model A's. I had a car at age 14-21 years and I rewired that car when only 15. I was troubled by the diagrams then too. The diagrams in the link you suggested did not help me either. I humbly suggest they aren't correct, but I'm no expert.
The original 1928 wiring of the ignition portion of the Model A was modified over time. You can refer to the service bulletins for that info, but the final diagram is still a bit confusing because of the representation of the ammeter. When I looked at the diagrams I was mentally viewing the firewall as if standing in front of the car. If the diagram does not show the face of the ammeter with the plus and minus scale, then a novice like myself can be confused as to where to put the two wires that go to the ammeter. If the diagram shows the ammeter face then one is viewing the diagram from the seat of the car! Which is it, dang it!
Yep it's confusing, but you can buy a nice diagram (large) from Snyder's for a few bucks and hang it on the wall. It shows the proper ignition system which evolved over time. The most important change was that earlier car's ignition problems were harder to diagnose when there was ignition trouble.
After a small modification (service bulletin) that moved the power source for the - neg side of the coil from the solid yellow wires, the discharge side of the ammeter, to the + charge side, the yellow with black stripe wires in the terminal box ... the proper opening and closing of the distributor points causes the ammeter to flicker. This flickering instantly tells a mechanic that the points are receiving current and thus pretty much eliminates all the circuitry and components from the battery up to the distributor points as being part of any ignition failure. (whew, that's a mouth full)
Pretty slick huh? Henry moved one end of a short wire and saved a lot of diagnosis time for the Ford dealerships.
The odd thing about the A's ignition for us modern folk is that it is a positive ground system with the ignition switch wired into the ground side of the ignition coil. More modern autos are negative ground, as stated in a previous post, and have their ignition switch wired into the source side of the coil.
I wired my car as the evolved, final diagram shows. And I bought the Les Andrews red service manual from one of the suppliers. Then the ignition trouble shooting method he describes in his excellent manual works like a charm.