97 E350 7.3L Instrument Cluster Testing? No Gauges

[harry989]

Hello guys, I have a 1997 E350 7.3L The only add on is a wheelchair lift in the rear. I seem to have lost my instrument cluster. A few months ago the gauges started fluctuating alot or not working at all. The Instrument cluster lamps started working only half the time, they would come on/off when we hit a bump etc. I can't find anything anywhere that tells me how to test the cluster or anything that gives me the voltage values for the wires coming into it or which ones the ground wires are.
Does anyone know how to test the cluster and/or know the values of the wires going into the cluster

Thanks in advance