Bad gauge/sending unit or bad thermostat.

[fordkid88]

What are the odds that my temp gauge or sending unit is bad vs my thermostat?

I went to job 25 minutes from my house, alot of highway use, my temp gauge was working fine good heat everything. I went to the next job, 20 minutes away, my gauge didnt move at all, I had good heat and the truck ran fine.
End of the day I drove home, it took 40 minutes to get home, a lot of highway driving with heavy traffic and a lot of stopping, heat is fine, truck ran normal and the gauge barely got to N on normal after a half hour. Now my oil pressure sending unit doesnt work and I have to fix that, the thermostat and coolant were changed in march. The thermostat is a failsafe one. I just think its weird that I have heat and the truck seemed to run fine.

 

[Chikar]

Well, if the thermostat wasn't working properly I wouldn't expect you to have much heat so I guess I'd say it's the gauge or sending unit, or their associated wiring.

 

[surf]

I replaced my temp sending and put a failsafe stat in my X and at first my temp gauge sat dead center after in warmed up. After a few weeks I could see that the gauge would climb towards center and then fall as the stat opened to sit right around the "N" on the gauge. I think the failsafe stats just open sooner than it should.