The Alladin system has NOTHING to do with the dash FUEL gauge. Monaco Fuel tanks use a drop in fuel sending unit that has calibration pots(screws). You fill the tank to full and then turn the calibration screw to just when it reaches the full mark. Now, Some also have the 1/4 (or 1/8 wherever you want it to send at) tank low fuel system also and it also has an adjustment screw on the sending unit to calibrate the 1/4 mark for the low fuel indicator. These sending units will have 2 of those screws instead of 1. From your age and description, you need a new fuel tank sending unit.
Your tranny gauge probably just has the wire corroded or off the sending unit. The sending unit is on the bottom of the tranny and if you know what it looks like, easy to spot. Now to the voltage. IF the dash system shows 18 volts but with a Handheld Volt meter you see 13.2 or what is supposed to be the correct voltage, then the voltmeter gauge is bad. BUT, explain what you mean by "battery Gauge" and I will assume you mean the DASH voltmeter. Where is this battery gauge? Doug
Yes the voltmeter.... my biggest complaint on the fuel guage is that its not consistent, sometimes it will read different everytime you turn the key on...i did get the tranny guage fixed, wire came off of sensor
Run a 12 gauge wire from the good frame ground to the ground connection/s on the back of the instrument cluster harness. Monaco's had a problem with weak/inadequate ground to the dash cluster. IF that fixes it, good. If NOT, then you can rule out a ground problem. Doug