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Subject: Ammeter polarity

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Charlie Rohlfing    Posted 09-12-2017 at 16:51:06 [URL] [DELETE]        [Reply] [Email]  
  • Ammeter polarity
  • Hey guys, I have an easy question ... which side of the ammeter do I attach the wire coming from the solenoid? It's a late-serial 1951 8n, all original factory 6-volt positive ground set up. Thanks!

    Tim Daley(MI)    Posted 09-13-2017 at 05:06:50 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Ammeter polarity
  • HiYa Charlie-
    We will assume you have a newer aftermarket style ammeter with the two screw terminals by your question. As stated, if readings are bassackwards -that is, negative readings when running, the wires simply just need to be reversed on the gauge terminals. No harm will occur if not right -no 'polarity' is required. The original 8N wiring utilized the AUTO-LITE Voltage Regulator, as shown in the picture below. FORD TRACTOR first used the -20/+20 AMMETER with screw terminals only on the first 4000 early 9N tractors, then released the "LOOP-STYLE" induction ammeter also shown in the picture below which now had the -30/+30 scale. Here is the LINK to JMOR's Wiring Pictograms as well to help better visualize the set up. Also, the I&T F-04 Manual, '39-'53 MPC, and the 8N Operator's Manual all have the wiring schematics complete with the original color-coded harness wires labeled. If you do not have the original cloth covered/color coded wiring, or a DC newer, exact-as-original wiring harness, do not assume wire colors are correct. The best procedure is to get the wiring schematic and do your own wire tracing and continuity checking to be certain all is right with the world before applying power and risk letting the smoke out of something if it is not correct.

    EARLY 8N WIRING, photo courtesy of Steve Dabrowski:

    Tim Daley(MI)

    K.LaRue-VA    Posted 09-13-2017 at 23:26:58 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Ammeter polarity
  • Wow! Wish I'd seen that photo a few years ago. I've been turning the light switch so fuse is up, and can't seem to get the wires to lay any way that looks right. Didn't occur to my sense of symmetry to turn the switch sideways. Might even make it easier to replace fuse. Somebody may find evidence that this isn't "original" but it sure appears to work better.

    K.LaRue-VA    Posted 09-12-2017 at 21:46:06 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Ammeter polarity
  • I started to respond with "the back side", then felt so guilty, had to go out in the rain and look at my 8N. Unfortunately, a big mud daubers nest is covering the whole back side of my ammeter. Even without that in the way, most of the wiring is cleverly concealed behind the tool box. I'm pretty sure the yellow wire from the solenoid goes to the ammeter terminal closest to the steering column, and the outboard terminal goes to the junction block. As others have said. Try it and if the gauge reads backwards, swap the wires.

    36 coupe    Posted 09-12-2017 at 20:01:00 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Ammeter polarity
  • Read your owners manual.Use the gear oil listed 90 weight.

    Bruce (VA)    Posted 09-12-2017 at 16:53:30 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ammeter polarity
  • Can't remember......

    Just Google "wiring diagram JMOR"

    Don't worry if you get it backwards. Won't hurt anything; it will just read backwards!

    Tony    Posted 09-12-2017 at 19:02:12 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ammeter polarity
  • Yeah, just hook it up if it reads discharge with the engine running and the generator charging reverse the leads. Some amp meters have the hot side post marked with a dab of red paint.

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