My 1688 has had multiple issues over the yrs too. Have taken the connectors apart and sprayed electronic cleaner on them would occasionally help but the small pins eventually corroded to bad so that I had to bypass some. It seems that connections that have constant voltage will corrode much faster then "dead" connectors. Last year one of my multiple wire round connectors under the console shorted out and burned crispy. Luckily I cot things disconnected before starting a fire. (Well maybe the ins. check would have been better?) Prior to the short I was having warning lights come on when the key was turned off and the only way to keep the battery from draining was to unplug several fuses. I did finally change the cab solenoid last year after doing a lot of rewiring and seemed to have solved most of the gremlins, except now the AC doesn't work. I must've gotten 2 wires switched. I remember that when I was trying to rewire it that I would hear the AC clutch click when certain connections were made. Will have to do a little more work I guess. 

My advice would be to pull one fuse at a time to see if you could get the light to go out. You may then be able to start tracing down the culprit connection. I should have used dielectric grease years ago when I first noticed corrosion, which may have prevented further degradation. Good luck, you may need it!