i think my water temp gauge is messed up. here's the situation: when i start my 4runner from being parked overnight (low 50* overnight), the water temp gauge reads cold (lowest position). after a 10-15 secs, the gauge jumps to a normal reading in the middle. the gauge doesn't move slowly. i feel like it has two positions - cold and normal.

i even installed the flex-a-lite electric fan and let the truck idle for 15 minutes. the gauge never left the normal position.

so, what could be the probably? bad sender unit? where is the sender unit located?

btw, it's a 88 4runner with the v6/5-speed setup.