[C320-list] Temperature Gauge

[Wandering Star]

I have a Yanmar 3GM30 and 2000 Catalina 320, sail #707.

Was out sailing last weekend and after returning to the dock and the engine was cooled down, I noticed the temperature gauge was stuck on 160. This is normal temp when I’m motoring.  

Today I disconnected the sending unit wire, engaged the ignition, and the needle immediately dropped from 160 to the left below 120.  Wondering if I needed to go check the sending unit wire I decided first, to start the engine and see what happens.    

As the engine warmed up, the needle on the gauge rose to 160. I turned off the engine and assumed the needle would lower itself back down to 120 but it was stuck on 160 again. The only way I could get it to drop back down to just above 120 was to engage the ignition and it would drop incrementally back towards 120. But only if the ignition was engaged. I did this over about half an hour.  

Does it sound like I need to check the sending unit wiring? Or could this point more towards a faulty gauge?  
Clearly, hoping just replacing the gauge would suffice as electrical is not my strong suit. 
Sara
Wandering Star 
Seattle 
2000/707


Sara S.
Sara S.