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In going through the instrumentation on my '39 Six, I have been trying to get everything back to original and functioning. My last hurdle is the ammeter gauge. The one in the car when I bought it, is 'pinned' in the overcharge position regardless of key on/off. I found a cluster (gas/ammeter)for a 1940 online and, although the face is ever-so-slightly different than the '39, the internal gauges themselves look the same. The 'new' ammeter centers nicely on zero charge and seems to move freely if the gauge is gently shaken. My question is: how can I test it to see if it is functioning before going to all the trouble of installing it?? I am somewhat 'DC challenged' but I have a 6 volt battery and a 10 amp 6-volt charger on my work bench. Is it possible to wire this up to show the charger's input on the gauge without hurting it? I am PRESUMING (dangerously) that the cluster itself must be positively grounded to the battery and then possibly a loop from negative to both terminals on the gauge, with the charger in the circuit??? Also, one of the terminals has a red '6' on it. Am I correct in assuming that would be the negative (hot side)??? I know there are some electrical geniuses out there who might chuckle at the simplicity of this, but I'd sure appreciate a 'how-to'. Many thanks

The ammeter or battery charge indicator as Packard called it is placed in series with a load to make it read. It will not be harmed if hooked up backwards as it will still work but just read backwards.

To test yours, use your battery rather than the battery charger and with a wire from the battery negative terminal place the ammeter in series with a known load. Connect the other side of the load to ground. Here are a few common and easy to access items for which Packard was kind enough to provide a load reading. The 39 six chart is slightly different than the 40. Because Packard was explicit in saying it is not an ammeter but rather a battery charge indicator the scale reading may not be linear. All you are interested in is that with the load hooked up the meter deflects. Correct terminal selection on the ammeter with only a load and no charging capability would have it deflect to the discharge side. If it reads to the charge side just reverse the wires on the ammeter.

From the specs I find for 39 it says the six generator is a third brush type so they don't give charging specs -- just that the generator is capable of putting out 30 amps when cold and 25 when hot. The 40 specs give a setting of 34-36 for the regulator so I would imagine that somewhere around 35 amps would peg the needle on your 40 ammeter.

If you want to get an idea of where on the scale the needle will go with a known amp load, you could add a regular volt-ohmmeter in series with the ammeter and test load. It needs to be capable of reading 10 amps if using a heater motor or something off the Packard charts for a load. Generally there is a different jack on the meter the red wire will plug into for directly reading that high of amperage. Don't use it for testing anything over the max rating of the meter (like horns) or the fuse inside the meter will blow. Once connected in series, the meter will give a reading and the ammeter needle will deflect to somewhere on the scale. You can make a note of the location so you will have an idea what would be normal in operation.

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