Testing heat sensor #278 / 000194

[seadoo@19072]

Recently had to rebuild top end of 1994 SeaDoo GTX. Piston seizure. iniatally caused by oil injection hoses to rotary valve intake disinigrated. I have a question as to why the the heat sensor did not sound the buzzer to warn me. Does the epansion of the rings and piston happen so fast that the heat sensor can't react? I tested my heat sensor with a pan of boiling water and a ohm meter, (not digital, gotta use what I got). After the water began boiling, The ohm meter's needle, set at 1K, went to 200K and held there. Is the #278 / 000914 a resitor type sensor or is it a on / off switch? If it is a resistor type, would not the buzzer start off at low volumn and build? I was expecting it to be on / off switch and the buzzer woul activate at full volumn. By the way, the buzzer works. Scared the bejeeses out of me when i tested it. Final question: Does it seem that my heat sensor is OK? THanks for your thoughts.

 

[Sportster-2001-951C-Stock]

I assume 2-stroke engine, possibly 787?

Heat sensor is activated if cooling water flow is compromised and the entire area is heating up. Probably it never even gets near hot enough when plenty of cooling water is flowing.

The piston can and will overheat and melt if the lubricating film fails for some reason, probably the cylinder sleeve doesn't get much warmer than normal due to the high volume of water being pumped through.

Periodically make sure the block drain isn't clogged by sand/debris, water exiting through the block drain helps to keep the lower section cool so when that drain is blocked causes lower section runs too hot.

Heat sensor is an on/off switch as far as I know, should show high resistance normally then low resistance (meter detects current flow causes ohmmeter needle to move up scale, indicating low resistance) when the switch closes.

Ir's purpose is to try detecting when water flow is impeded b/c heat will build. Normally this sensor will detect loss of flow and sound the horn BEFORE engine damage occurs. To test the horn function, ground the wire.