ZD326 Possible temp sender problem?

[JED COOPER]

My temp gauge normally runs about mid scale. Last week it started moving up to about 2/3 towards hot, but it'll stay there for a while then drop back to normal. It'll repeat this during a 2 hour mowing. I've changed the coolant(50/50 premix diesel rated) every year, new radiator cap last year. Mower is 14 yrs old with 2200 hrs. Radiator is clean and belt is tight. Upper hose is firm when running, so it's making pressure. I checked the engine temp while running at the temp sender with a IR gun and also near a couple freeze plugs and it's running 180 degrees. I'd suspect the sending unit as opposed to the temp gauge. Block temp doesn't change even after running a couple hours(with IR gun check)
Thoughts?

 

[whitetiger]

My temp gauge normally runs about mid scale. Last week it started moving up to about 2/3 towards hot, but it'll stay there for a while then drop back to normal. It'll repeat this during a 2 hour mowing. I've changed the coolant(50/50 premix diesel rated) every year, new radiator cap last year. Mower is 14 yrs old with 2200 hrs. Radiator is clean and belt is tight. Upper hose is firm when running, so it's making pressure. I checked the engine temp while running at the temp sender with a IR gun and also near a couple freeze plugs and it's running 180 degrees. I'd suspect the sending unit as opposed to the temp gauge. Block temp doesn't change even after running a couple hours(with IR gun check)
Thoughts?

Change the thermostat.

 

[DaveFromMi]

Check all the electrical connections and leads between the sender and the gauge.

 

[GreensvilleJay]

'up and down'.... change the stat.... it's 'sticking' a bit,then releases, over and over.....
Just be sure you put it in the correct way.....

 

[JED COOPER]

New temp sensor fixed the problem. Temp gauge needle will rise to normal now and hardly move.
Temperature here reached 85 yesterday and gauge stayed normal after mowing 3 hours.