Temperature sensor any ideas

[Phil Read]

My temp sensor does not work. If I remove the cable from the sensor and earth it the temp needle goes up to hot. I have replaced the sensor but it still does not work. Any ideas?

[RogerH]

Hi Phil 

test the continuity of the wire from the thermocouple to the gauge.

Test the continuity of earth from where the thermocoluple screws in to the battery neg terminal

With the thermocouple in  a pan of hot water can you see a resistance change between that and when cold.

Roger

[Mike C]

Reading low?-In mine that was caused by a faulty voltage stabilizer.

[astontr6]

1 hour ago, Phil Read said:

My temp sensor does not work. If I remove the cable from the sensor and earth it the temp needle goes up to hot. I have replaced the sensor but it still does not work. Any ideas?

I had a load of trouble with my original sensor and then bought one from Moss and the reading got worse? I then carefully cleaned up one of the hexagon flats and noticed a part number. I then spoke to Moss they said that the one that they supplied was an equivalent. Moss quality???? Alarm bells rang in my head so I spoke to Caerbont Automotive Instruments. Yes we do manufacture that Smiths part number TT4803-00A, Temp Transmitter. I was was not happy about the price  but I did buy one and it worked as  it used to and that was 5 years ago. They also make the infamous Speedo gear box another very trouble some part as original # BG2401-05 on the original tooling. NB. I had also replaced my voltage stabilizer with a solid state one.

Bruce.

[RobH]

Your test of earthing the wire shows the gauge and cabling are OK. 

 If you have no reading at all it means either the sensor is open circuit or there is no electrical earth on its body. Try touching the wire to the body of the sensor. If the gauge shows hot, the sensor itself is at fault. If the gauge does not respond then the sensor body is not earthed.