temperature switch

[flyguy]

I Have A 1977 Mercury 1750. When I Rebuilt Transom I Disconnected Wires. I Have Everything Back But Can't Figure Out Temp Switch. Its A Green And White Wire Coming From Temp Alarm Horn. I Connected It Directly To The Temp Sensor In Head And As Soon As I Turn The Key The Horn Sounds, So I Must Have Wiring Wrong. Any Help Would Be Greatly Appreciated.

Thanks

Flyguy

[Poida]

Don't know anything about the model of boat you are talking about but
1st disconnect the horn from the sensor. Does it still sound.
2nd If no sound the current must be true through the temp switch. Test the temp switch with a continuity meter or a 12 volt tester, 1 lead on the sensor connector the other on the engine, from an auto shop to see if you have a closed circuit. If the circuit is true you have a faulty switch.
Poida

[Tim B]

There are some temperature sensors that will be sensitive to polarity. Thermocouples are notorius for this. Is there any possibility that the polarity is reversed?

Tim B.

[flyguy]

did continuity check, with wire not connected there is continuity, so i guess its stuck open. can polarity be reversed if there is only 1 wire?

thanks

mark

[Poida]

Not likely the engine is used as earth (ground) normally negative or also known a 0 volts.