Have a single 4500. When I turn it on without anything connected to back (no sensor input) the tank 1 AD_VALUE is 27 and tank 2 is 3668. When I connect the sensor wiring to the back of the 4500, tank 1 is 26 and tank 2 is 250. Just got done trying to calibrate tank 1 by first draining all of the gas and then filling it up 5 gallons at a time AD_VALUE was always around 27. The analog gas gauge was always accurate. I have not hooked up a ohm meter to the sender wire yet but it seams strange that the AD_VALUE never really changes much for tank 1.

Thanks for your time.
Mike