temp warning light on all the time

I have a 2003 Johnson 4 stroke 90hp. This spring when I put our pontoon in the water every time I start the engine the warning lights and buzzer go through there checks but then the temp warning light remains on. is the there an easy way to check this out? I over 40 years of experience as an auto tech. so I know somewhat of how to test circuits out.

Re: temp warning light on all the time

try to unplug the sensors & start motor.and plug one in at a time.

Re: temp warning light on all the time

Just had a similar problem with son's V Merc which has two temp sensors.

Would go thru the initialization and got the solid and intermittent beeps and lights indicating that temp and oil sense modules were ok during startup just like you.

But noticed a dim light glowing constantly (with the engine running) and a low level audible alarm. As time progressed (engine on time) things got brighter and louder.

In short, one of the thermal sensors was going bad. I thought this was a snap action switch that was on or off but now I don't know. I disconnected that side and the problem immediately subdued. I measured resistance between the output wire of the sensor and ground of varing value of less than 100 ohms depending upon temp.

When he gets the new one installed, I am going to dissect the failed unit to see why we got those peculiar responses.

Mark