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Subject: 8N AMP Gauge

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Kevin Blake    Posted 01-15-2018 at 12:12:08 [URL] [DELETE]        [Reply] [Email]  
  • 8N AMP Gauge
  • I have a 1947 8N s/n 3040, it has what must be the original amp gauge.
    But it doesn't show 2 contact connections, it shows a single wire running through a metal loop on back of gauge. Did they use the electrical fields back to detect current or is mind just not hooked correctly? I don't see anything on back to hook to. Any help would be appreciated.

    Tim Daley(MI)    Posted 01-15-2018 at 14:09:42 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8N AMP Gauge
  • HiYa Kevin-
    First, are you certain you have s/n 3040? Where are you finding this number? Make sure you aren't looking at a part number. There's no doubt you have an original induction (loop) style ammeter, but often fellas look at a part and see a number and think it is the s/n. The serial number on your 8N will begin and end with a STAR (*) symbol and have the "8N" in the number prefix. Next, the original AMMETER on the first 4000 9Ns were a 4-screw terminal 20/20 type. Two terminals were for the wires, two were for the mounting bracket. At s/n 9N-4000, roughly, Ford then changed to the INDUCTION STYLE, often called the LOOP AMMETER. The lone wire, no splice, fed thru a loop on the back side of the gauge and electrical current was measured by induction. If you download a copy of WIRING PICTOGRAMS by JMOR from our HOW-TO's forum, you will see exactly how to wire your 8Nas original. Pictures below may help as well. You can test your LOOP Ammeter with magnet simply by moving it across the face bezel and if the needle moves, the gauge is good. Another test is to connect it to a 6-volt battery and run one wire thru the loop. If it results in a bad gauge, and you want to keep it original, email me as I have about 2 dozen good loop gauges in a coffee can stored away. Today, the new aftermarket ammeters are the screw terminal type -see pictures. they only have two screw studs acting both as the wire conductors and the mounting bracket supports.





    ...and the BACK SIDES...

    Tim Daley(MI)

    TheOldHokie    Posted 01-15-2018 at 13:14:30 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8N AMP Gauge
  • It's an inductive pickup. Michael Faraday demonstrated that effect in 1831 so Ford had a century plus to figure out how to make a connection-less (inductive) ammeter ;-)


    Bruce ( VA)    Posted 01-15-2018 at 12:33:27 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8N AMP Gauge
  • It's a loop detector. No connections needed.

    Kevin Blake    Posted 01-15-2018 at 13:43:25 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8N AMP Gauge
  • Ok great, thanks for the input. It's not working and I would like to keep anything original on my tractor if possible. Is there anybody that can refurbish these, if not is their anyone who sells them? Maybe I could fix it myself, any history of things to try, it does show some deterioration inside the window glass.

    Tim Daley(MI)    Posted 01-15-2018 at 14:17:02 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8N AMP Gauge
  • Kevin-
    See my reply above. I have several original LOOP Ammeters if you need one. Bruce's estimate is a little low. I had an ammeter and an oil pressure gauge restored at Bobs back in 2003 and the cost was over three times that amount for both. Now, there are other places that also will restore gauges. Steve Dabrowski used a place in Ohio, I think, for both is early 9N and early 8N gauges. I can't recall their name and contact info nor how much he paid, but perhaps Steve will see this and chime in. My email is open...

    Tim Daley(MI)

    Kevin Blake    Posted 01-24-2018 at 13:26:03 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8N AMP Gauge
  • Thanks for all the help, Tim, having email issues, I can revive email but not send. Can you email a contact number to me and I will call you

    Kevin Blake    Posted 01-15-2018 at 15:36:37 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8N AMP Gauge
  • You guys are a great source of help.
    Could I get pricing and pictures? Do you have original oil pressure gauge as well?

    Tim Daley(MI)    Posted 01-15-2018 at 18:12:04 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8N AMP Gauge
  • Kevin -you can email me and we will discuss parts and pricing off the board. Just click on my underlined and highlighted name and it will take you to your email provider. Yes, I have an original oil gauge as well. Let's first determine if your ammeter is bad. You might have a bad voltage regulator and/or a bad generator. Does the tractor start and run now? Is it still the 6-volt/positive ground setup? If so, how old is the battery and do you still have the original AUTO-LITE Voltage Regulator as shown in the picture below? Do you have the essential 8N Owners Manuals? Let's perform a true root cause problem solving method before making any decisions or before buying any new parts. We're all in this together and are here to help...

    ORIGINAL EARLY 8N AUTO-LITE VOLTAGE REGULATOR; -photo courtesy of Steve Dabrowski :


    Tim Daley(MI)

    36 coupe    Posted 01-18-2018 at 09:39:52 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8N AMP Gauge
  • I put a length of heat shrink tubing on the wire where it goes thru the ammeter loop.Look for rotten insulators on metal bracket meter mounts.Plastic brackets are better.The last SW meter I changed out had rotten insulator bushings, a fire hazard.

    Bruce (VA)    Posted 01-15-2018 at 13:52:00 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8N AMP Gauge
  • Last time I checked, cost to rebuild it was something like $200. That's fine if you need it to complete the restoration on your 1936 Auburn, but probably not worth it for your 8N.


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