888 Temp Sensor

"I have a 1977 Sea Ray with a

"I have a 1977 Sea Ray with a Ford 302 and Mercruiser 888 sterndrive.

I bought the boat a few weeks ago and was told the temp sensor doesn't work. There is one wire going to the temp sensor, and a free brown wire not attached to anything right next to the sensor. Should this be grounded to the block? I'll try to post a pic tonight."

"If you have a voltage meter a

"If you have a voltage meter and can measure ohms then set the meter to ohms ( r x 1 or 10 or the one that will beep.
connect one meter lead to the brown wire and the other lead to the back of the temp guage . The terminal on the guage for the sender wire should have a letter on it (S) I belive. You may see a brown wire attached to it allready. There should also be a purple wire or the same color that goes to all guages. ( power).

If it is the correct wire and the guage does not work when connected then you need to find out wich is defective, the guage or the sending unit.

If you jump the sending post on the guage to ground very briefly with your key in the on position ( only for this test)it should PEG the guage. At least you will know the guage works.

The sending unit is nothing more than a variable resistor. when heat is applied the resistance changes. The range of the sending unit is if I remeber correctly 60-80 ohms to 240 ohms.

I think cold is 240 ohms and hot is 60-80- ohms.
Or visa a versa?? I forget........LOL

If you put a ciggarett lighter under the sending unit when removed from the motor with a ohm meter atteched to the center post ( one lead) and the other lead to the threads of the sending unit you can se the ohm reading and when the flame is applied you can watch it change.

Hope this helps."

"thanks, i'll give that a

"thanks, i'll give that a shot tomorrow!"