Hi All,
My Car has been on the road now for about a year since I restored it during the lockdown. I would like the ammeter to work as it never has since the rebuild. The car was converted from positive to negative earth and I was told to just swop the two main wires on the gauge but nothing happens! I guessed it might be a faulty gauge so we have just tried to fit a new ( cheap type plastic bodied) but this does nothing too. Is there a trick I'm missing ?
Cheers Ray

 

As far as I am aware the power comes from the alternator or Dynamo to the ammeter before passing on to the battery. Have you tried putting a test gauge/ volt meter on the wires going to the ammeter to test the flow of power. I know when my ammeter is working there is hardly any movement in the needle unless as happened recently that my rectifier broke. I was not getting any charge from the alternator and the needle was showing a big "D" for discharge. ie the battery was supplying all the power and draining. When the alternator was repaired I was getting a big "C" for charging as the alternator was charging the battery but once the battery was charge the needle was back in the middle with no movement.
Another way to check the ammeter is to actually disconnect the two wires on the alternator and then start and run the engine which will then only be running on battery power. Turn on all the lights, wipers, heater fan and radio and If the needle goes to "D" then the ammeter is working fine.

 

As Cass said, one way to test the ammeter is to turn the headlights on without the engine running. If the lights come on, there's current flow and the ammeter should swing to the discharge direction. If it doesn't, I'd suspect that the ammeter has been taken out of the circuit, for example by connecting the + and - lines to the same terminal on the back of the meter. If the meter were burnt out, it would not pass any current.