Terminal 15 and Current for Fuse 9, Not enough juice? Options

[jwilliamadams]

Not sure where to go with this, or if I really even have an issue at all. This has come about because I started researching into why my voltmeter (old one and now a new one) drops in volts when I apply the brake lights or when I turn on the reverse lights. If the engine is not running but the ignition is on I get 12 volts on the guage. Applying the brake lights or reverse lights drops the guage to below 12. Like to 10. New battery. With engine running at idle of course I have higher than 12 volts, but still experience the voltage drop (just not as much).

All the guages, the reverse lights and the brake lights are connected to fuse 9. Fuse 9 gets its juice from terminal 15 of the ignition switch, which also feeds directly (fuse-less) to terminal 15 of the coil. So I started to wonder if terminal 15 on my ignition switch is feeding enough juice to this circuit.

To test this idea I jumpered from the feed end of fuse 10 (which is directly connected to the battery) over to the feed end of fuse 9 and presto, the voltmeter does not drop hardly any when I apply brake lights or reverse lights.

I checked the lead from the battery to my ignition switch that feeds terminal 15 of the switch, and it seems fine. It's as if something is going on inside the ignition switch and a full connection is not being made from the lead to terminal 15.

Has anyone researched into anything like this? Since circuit 15 is such an important one, feeding the coil and all, I am a bit curious why the voltage is so unstable within.

Thanks!