Hypoid previously posted:
"I just looked up a wiring diagram. As I suspected, voltage feeds through the gauge to the temp sensor in the engine. The sensor has a variable resistance that is dependent on it's temperature. The gauge reflects that resistive value.
Without any hands-on diagnostic, I'm taking a leap and saying that the sender has failed. I am thinking that the gauge and wiring are OK simply because the needle moves.
Maybe one of the yota gurus can chime in and tell me if the resistance increases or drops with temperature increase.
Just for giggles, leave the wire unhooked and turn the key on, see if anything happens."
"Judging from what you said that the gauge pegged just as you started it up. I am going to say that the temperature sending unit is on it's way out, not the gauge or the thermostat. The electrical connection could also be at fault, but the wire would almost have to be falling off the sender.
Gauges seldom bite the bullet, but sending units, electrical connections and thermostats do. Since you already have the T stat, it sure isn't going to hurt to replace it. The sending unit is very close to the T stat, so you might as well replace that, too. I bet your problems will go away.
BTW, you will probably need a Yota specific sending unit if you have the Yota gauges. Due to the varying voltages/resistance, etc. the brand of the gauges have to match the brand of the sending unit."
Thanks, guys. Looks like sending units are only about $12 or so. I'll go ahead and order one, and I'll replace the thermostat this weekend.
Pete, do you know if the unit just unbolts and bolts in? Does it sound like a job for PB blaster?