Richard, On my Cummins engine, there is one temp sensor feeding two gauges. Cummins instruments are all manufactured by VDO. The two gauges are wired in parallel, not in series. This setup would be common on a wide variety of instrument clusters and engines. There are two different sensor part numbers, one for systems with only one helm station and one for systems with two helm stations. The sensor resistance matches the VDO gauge gauge circuit resistance, and the correct sensor is needed to get the gauge(s) to show correct readings. The gauges have three terminals: B+, B- and signal. If you have one gauge with funky readings, first check all wiring, INCLUDING the B+ and B- (ground) wiring to the instrument cluster. If that doesn't correct the problem, swap the gauges and see if the problem follows the gauge or stays at the station. If it follows the gauge, replace the gauge. If it stays with the station, look for a problem somewhere in the wiring to that helm station's instrument cluster. If you have funky performance with BOTH stations, some gauge failures can affect BOTH gauges, but so can a bad sensor. It's easiest to start by changing the sensor. The sensor lives in a very hostile environment, so changing it every few years as PM isn't a bad thing. Hope this helps. Jim Peg and Jim Healy, living aboard Sanctuary http://gilwellbear.wordpress.com Monk 36 Hull #132 MMSI #367042570 AGLCA #3767 MTOA #3436