Temp. Sensor

[GrilloBurger]

Okay, I posted yesterday about some dissapearing coolant. I'm pretty positve that the fluid is not leaking internally. But my tempurature gauge is erratic. It's always on the line of normal and then teter totters closer to 'C' (never touching it though) then back to normal. The heat is coming out hot, and I have no A/C, hasn't been charged.
Could this be the a bad or corroded Temp. Sensor? If so where is it usually located. I've been browsing websites and none have a diagram. Any suggestion on where I can find the sensor, or websites that have picture and "How Too's"? Thanks.

-Jordan

P.S Could this also be a sign of something majorly wrong with my cooling system?

 

[Iron Weasel]

A bouncing gauge could be caused by air in the cooling system, but if that were the case the gauge would swing somewhat slow and it would also go down a little bit as air bubbles go past it and then back up to its normal spot when it was covered with coolant. If the gauge is moving fast and erratic, then it could likely be a sender or sensor.

Now, there are two ECT (Engine Coolant Temperature) "sensors". One is located on the front left (driver side) of the intake manifold. It's a 2-wire sensor and is damn near directly underneath the front of the throttle body. This sensor is the one that sends data to the PCM. There's also another ECT sensor, but sometimes also referred to as a coolant temperature sender, that sits above the thermostat housing. This one is a single wire sender and feeds the gauge.

The single wire sender is normally less than $10 and is fairly easy to replace and it's one of those parts that you just change since there isn't any way to repair it. The 2-wire sensor also feeds the gauge, but it's normally the single wire sensor that causes the gauge to freak out. You can pick up the ECT for around $15. Both sensors are easy to find if you look in the right area, but if you need help I can go take a picture of them and post them back up.

Single wire sender looks like this:

Two-wire sensor looks like this: