Temperature Sending Units

[FLcustom10]

I bought new temperature sending units (gauge and warning light) from O'Reilly's and could not get either of them to work. The light glowed softly all the time, the gauge showed the truck was over-heating when it wasn't.
I bought a replacement warning light sending unit from LMC and it worked fine. Then I bought a replacement gauge temp sending unit from Wes at Classic Heartbeat and it worked fine. I spent so much time trouble-shooting this - --- new thermostats, multiple bottles of coolant, when I just needed to get the proper temperature sending units from someone that specializes in these trucks.