Temperature sensor

[nodestination]

Got me a dilemma. I have twin 80hp Lehman. Lower station temp gauge never worked, but the upper worked fine. Now none is working on starboard. Portside works fine. I have a sensor in the head, expansion tank and on bottom of block. The gauge is hook up to some kind of relay(2). One is alarm, but have no idea what is the second for and which one sensor goes to temp gauge. Could use some help here. Thanks.

 

[RT Firefly]

Greetings,
Mr. no. Electrical problems are always fun (some sarcasm intended). The very first thing I do is check ALL connections for corrosion and/or tightness. That and integrity of any crimps/splices.

 

[nodestination]

Fix the problem -add fluid to expansion tank.

 

[RT Firefly]

Greetings,
Mr. no. Is the low fluid in the expansion tank a new occurrence? I check mine every morning before start up along with engine oil and transmission levels, belt tightness and a few other critical systems.

 

[BruceK]

Fix the problem -add fluid to expansion tank.

Interesting. FL120s,and I expect, 80s, have an air bleed valve at the top front of the exhaust manifold. It must be open when adding coolant to the expansion tank, fill until coolant appears at the valve.
Never open the valve with the engine running or it will draw in air,displacing water and causing overheating.