Re: Alternator & Ammeter

Posted by HH56 On 2016/6/9 13:45:26

Going along with what Kev just said this has been an issue before and no satisfactory answer yet. Some have tempted fate and kept the small ga wire for the alternator and others replaced the wire similar to your approach but live with the ammeter. If you didn't want to see a constant discharge you could also place a heavy jumper across the ammeter terminals so it always registers 0 and then use your light output signal to place an idiot light under the dash -- instant Clipper.

Referring to the 56 diagram and wires labeled #1 and #2. Normally the generator output is connected to the battery via the ARM or GEN terminal on the regulator and contacts in the regulator connect it to the #2 wire on the BAT terminal. That way the output goes thru the ammeter first and then on to battery via the #1 wire which connects to the battery at the solenoid. With your alternator directly connected to the battery at the solenoid same place as the #1 wire you are completely bypassing the ammeter.

The #2 wire is supplying almost everything in the car so if there is no charging coming into that side all the ammeter sees is the discharge. If the generator has output, then that being applied to the #2 wire in addition to any coming directly from the battery thru the ammeter lets the ammeter see what is happening -- either registering charge when the generator is keeping up with the draw plus delivering enough to the battery to keep it charged or a discharge if not. With your connection, even if the alternator is charging the ammeter can't see it.

With the direct reading ammeter in our cars it is going to be extremely difficult to have the output pass thru the ammeter safely. Even if you could replace the 10 or 12ga wire that is there now with recommended 6ga the ammeter is undoubtedly not capable of carrying 85 amps. It would be so much easier if the ammeter was actually a voltmeter calibrated in amps and fed via the voltage developed off a shunt resistor. You could just extend the wires and relocate the shunt resistor with a heavier one for the 85 amps if that were the case.

I don't know the internal construction of our ammeters. It is possible there is a small shunt inside that could be made external and larger but I doubt it. Maybe there is something an instrument place could do but I expect the cost would be considerable.