Thank you very much for the very helpful additional responses. I'm starting to see the way forward in solving the gauge issue, but it is different than I had first imagined. For those who may be interested, here are some recent details of my saga. I have characterized the gauge signal from the gauge control module. It is a pulse-width modulated 5 volt, 1 kHz square wave. Decreasing fuel level correlates to greater off time in the duty cycle. The gauge has a zener diode that limits the voltage to the air core motor. The coils in the air core motor are driven directly by a microprocessor on the gauge circuit board. The driver for one of the coils has failed -- a repair would entail a replacement of the microprocessor. This may be a design deficiency if the failure mode involves overheating of the chip because the coil current is near the maximum capacity of the microprocessor. The microprocessor is readily available from other sources off the shelf, but the code is most certainly proprietary to AutoMeter. I've attempted many times with no success to contact AutoMeter to see if I could obtain only the programmed microprocessor from them. It's a very long shot -- I would be stunned if I were able to buy it from AutoMeter. I could replace the microprocessor, reverse-engineer the code, and perhaps add external current drivers to the microprocessor outputs. Technically feasible, but very far from cost effective. At this point, for me it is enough that I know that the solution exists to repair the original gauge.
I am going to explore several possibilities going forward. One is the feasibility of transplanting a stepper motor into my original gauge housing -- there may be some packaging issues with this idea. Another is the purchase of the AutoMeter replacement if they remain available. A third is adapting the original gauge faceplate to the Speedhut replacement stepper motor gauge and reducing the Speedhut 270 deg. needle sweep to the approx. 120 deg. sweep of the original gauge. A fourth is a full replacement of all the gauges with the Speedhut versions. Maybe I haven't yet discovered the approach I will finally take.
In pursuing this project, I have become more impressed with Speedhut and have become aware of other vendors and suppliers, like Redline Gauge Works in CA, that also could be great resources in solving problems with gauges in the FGT. Any ideas or thoughts?
