In Reply to: 8N AMP Gauge posted by Kevin Blake on January 15, 2018 at 12:12:08:
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.
FORD-FERGUSON ORIGINAL 9N TRACTOR 20/20 AMMETER; SCREW TERMINAL TYPE:
FORD-FERGUSON TRACTOR ORIGINAL 30/30 INDUCTION (LOOP) STYLE AMMETER; AFTER S/N 4000:
FORD 8N TRACTOR DASH PANEL, BACK SIDE:
ORIGINAL 30/30 INDUCTION AMMETER AND NEW AFTERMARKET TERMINAL TYPE:
...and the BACK SIDES...