I have a 1994 C-220 and recently have begun experiencing problems with water temp. and gas gauges. The gauges do not work (remain at zero) if ambient temperature falls to 45 f or below. They will go back to normal operation as ambient and/or interior temperatures start to rise. Once working they will remain in working mode regardless of outside ambient temp. Also when they start to work the gas gauge will come on first followed by water gauge after a minute or so. At higher ambient they function fine. I do not have a wiring diagram and wonder if there is a voltage regulator that may be malfunctioning. Rest of the dash gauges are not effected.