L2550 temp gauge always shows Hot

[Ohio Farmer]

Temperature gauge on L2550 always goes to hot just by turning on key. Tractor is cold. Got 2 new temperature sensors both do same thing. Unplugged sensor with key on, gauge goes to zero. Checked wire for short to frame, ohm ok. Even took meter assembly apart, all look ok. Gauge worked fine 2 years ago, then intermittently started going to hot every once in awhile while mowing then back to normal. Now it goes to Hot by just turning on key. Even tested by putting 1000 ohm rheostat in line between meter and sensor. Adjusting rheostat make gauge move accordingly. Any ideas what would case meter to always read Hot?

 

[Roadworthy]

If varying the rheostat varies the reading the gauge appears to be working correctly. You are varying the current apparently more than the sensor in the block does. From that I would guess either the voltage arriving at the gauge is too high or the gauge itself is defective. Try setting your rheostat such that the gauge reads cold when you turn on the key. Leave the rheostat or a fixed resistor of that value in line as you run the tractor. See if the gauge responds normally as the tractor warms up.

 

[North Idaho Wolfman]

I would say more than likely the gauge is bad, the winding inside have probably shorted to themselves.
The second likely possibility is that the gauge wire has built up too much resistance either through a bad connection or even the wire itself, use a new jumper wire to bypass and test it.

 

[stumpcutter]

Did you use teflon tape on sensor? Sometimes it keeps the sensor form ground. Just a thought.

 

[BigG]

Did you use teflon tape on sensor? Sometimes it keeps the sensor form ground. Just a thought.

I'm amazed at the info that you find on here. Teflon tape as an insulator. Who would ever thought of that. Thinking like that is why it is so entertaining to read this forum. I have no idea if it is right or wrong but it is away to redirect ones thinking.

 

[Ohio Farmer]

I would say more than likely the gauge is bad, the winding inside have probably shorted to themselves.
The second likely possibility is that the gauge wire has built up too much resistance either through a bad connection or even the wire itself, use a new jumper wire to bypass and test it.

Gauge appears to work while varying rheostat. More resistance would cause gauge to show more on cold side. But who knows. Can new gauge be purchased?