sfsutton,
I'm not familiar with the voltage reducer you are using, but I wonder if it is suppose to behave this way normally, or could the load of your test light be causing this behavior.
Before I replaced this unit, I would use a voltmeter and see if it is actually dropping the voltage to 6 volts.
If that proves, I would test the gauge by pulling the wire at the sending unit. There are three options as I see it...bum gauge, broken sending unit or faulty voltage reducer.
I haven't seen the Fifth Avenue troubleshooting directions, but if they are complete and accurate, you should be able to determine if the gauge or sender is at fault.
Before you toss your new voltage reducer, make sure it is not working...with a volt meter!
Remember that when you probe the output side, you must have a load on it...a light bulb or something to draw some current, otherwise you will see the same value as the supply voltage (I think).
Lots of folks claim they have run 12 volts through the gas gauge for years without problems. If you feel frisky, you could prove the gauge and sending unit 'without' the IR4 in series. This would take that unknown out of the equation and get you back square one.
Just for grins, probe the ignition switch itself, when turned on, and see if incoming power is 'blinking'.
Stuart
