Amp Gauge problem

[Highbanked Hauler]

 I put in a low mileage amp gauge with the two wires in place and it doesn't work. I put the original back in which did work and now doesn't. Is there any way to test it??

[Nacho-RT74]

amm gauge is a very simple gauge... a copper plate what mooves magnetically over a shunt linking both studs. The mooving plate does have a pivot and the needle attached. Just that.

is easy to check if pieces are in place. As far pieces are in place and free movement, gauge must work

[Highbanked Hauler]

 Thanks, it must be a power or a ground problem then as the gauge looks new.

[Nacho-RT74]

not at gauge, ammeter doesn't get or need ground, is totally isolated from cluster.

if needle is not moving, no matter if D or C reading and ammeter is GOOD, power is not getting up to ammeter...

but ign key and main splice is AFTER ammeter, so must get D reading if some light or acc is on.

UNLESS you have an splice from alt to batt or related wires. That will bypass the ammeter

[Ghoste]

The fact that your old one used to work but didn't after swapping it back in would tend to make me think it wasn't an issue with the guage.

[scatpakrt]

Locate the large black wire at your bulkhead connector and check for burned terminals there. Although it is a black wire it supplies the output of the alternator to supply power to everything. There is, on my 71 B body, a factory welded/soldered splice under the dash from the bulkhead on the inside of the car, and then it goes to the amp meter black terminal. Other side of amp meter has a red wire to starter relay "Batt" terminal. Check, with car running, for 12v + on both terminals of amp meter. Use a good ground with black portable meter lead and red lead to both amp meter terminals one at a time and see if 12v + is there. You should see 12v on the red wire to the starter relay present with just the key on, but the black will require the alt. to be running to output 12v.

Hope this helps your troubleshooting.

P.S. No ground involved on amp meter circuit so don't go chasing bad grounds for ampmeter problems.