Temp Gauge Issues

[larman]

I have twin diesels on my boat and neither engine has a correctly functioning temp gauge. Port engine spikes when I turn on other accessories and especially my navigation lights. Temp is inaccurate before anything is turned on anyway. My starboard gauge gets pinned at 250 degrees until I tap it. Obviously I have an electrical issue but where do I start?

 

[Bud]

I had a similar problem. Power for my Niad Stabilyzers was hooked to the circuit for starboard engine (gauges and solenoid) The solenoid valve in the Stabilyzer was shorted to ground causing low voltage and drawing current through gauges specifically the temp gauge ( must be low resistance sender). When I disconnected Stabilyzer circuit gauges were fine. I replaced solenoid valve assembly and put in power relay for stabilyzers activated by Starboard engine on breaker. (hydraulic pump for stabilyzer is on starboard engine)

Bud

 

[larman]

How were you able to determine what was causing the issue?

 

[Bud]

I was inspecting the instrument panel and saw the power wire from the stabilyzer system hooked to the power on panel. I disconnected the stabilyzers and saw the instruments went back to normal.
Bud

 

[C lectric]

Check the + and - leads that supply voltage to the panel. If they are in poor shape then none of the guages will work properly.
If need be follow back to the busses and battery switches that supply them.
Loose or oxidized connection can cause this.

For specific guages check also at the sender terminal for clean tight connections.

If there are questionable connection creating excessive Vdrop then as loads are turned on or off it can create too large Vchanges for meters to allow for.

When I got my boat a long time ago my nom working guages started working as I cleaned terminals and often reterminated wires with new crimp on ends.