hockey651- your on the right path, look at the depth/air/water module. first thing I would check is for a solid ground. Then make sure you have 12 volts to the module. ( a while back i realized the factory had wired the module to always have power on, which led to burning out the transducer for the depth guage. I recommend you find an accessory voltage source. If i remember correctly the purple wire on the decc is acc power. Easy switch of the 12 volt wire. next check the multiplex wiring between all the guage parts. You may want to look at the "Digital instruments installation guide" in the maintenace section. check out page 12 it will explain how all the connections are very important for all the info to work right. Thats what sucks about CAN (controller area network) multiplex. one bad connection in the chain and all hell breaks loose. Your only looking at 5 or so connections. in doubt- unplug one at a time check for moisture or corrosion and reconnect, make sure the terminal end plug is installed. good luck.
