Temp gauge all over the place!

[johnwohl]

So today i'm driving and I notice my temp gauge is at the high white line (not into the red) so I crank the heat, which usually will cool a car down pretty quick but it had no effect. I get to work and pop the hood and my engine fan isn't on which is odd, it usually goes on after 1/2 temp. So I turned the car off and resolved to see if I could fix the problem on break.

A buddy of mine came outside and we started the car and the temp gauge rose to half way faster than usual and then continued to climb a bit settling at a bit less than 3/4 (engine fan didn't turn on). I pulled the ac fuse and pushed the ac button to turn both fans on and they both went on fine put the temp gauge barley dropped. Then I gave it a little gas and the gauge pretty much bounced from 3/4 to 1/2 and then back up. WTF. There's no way my car is running that hot with BOTH fans on. We didn't figure it out obviously on break.

Then when I got in to go home the gauge shot up to operating temp not even 3 blocks from my work, and continued to be odd. It would climb a bit at a light (still both fans on), but then as soon as I hit the gas (not necessarily moving even) it would go back to normal. I know it's gotta be some sensor or something but which one?? I have no idea. Do you??

 

[Defiant]

If you're cooling okay, it may be either the temp sender dying, or a short in the wire feeding it.

 

[johnwohl]

It seems like I'm cooling ok, but it doesn't seem like the engine fan is coming on when it should. Is the temp sender/switch what controls that?

 

[jumpfroggy]

"Then I gave it a little gas and the gauge pretty much bounced from 3/4 to 1/2 and then back up."

This seems odd. It seems unlikely that the coolant temp would vary immediately with the gas pedal (takes a while to heat liquids, depending on specific capacity). I had weird problems with an old car when the head gasket went. A side effect is that it spit out coolant, looked fine at normal temp, then all of the sudden would shoot up to redline temps when the coolant got low.

Could it be your coolant is low? I'm thinking maybe the coolant is too low to flow properly, so the temp sensor is coming into contact with the coolant properly, and a surge in flow (like hitting the gas, which would spin the water pump a bit?) might make it "splash" onto the sensor for a second.

If the coolant were low and the temp sensor hit an air pocket, it would not register the correct temp setting and may show varying incorrect temps, which may not trigger the fan. Check the coolant level, maybe burp the coolant system, check for head gasket leak symptoms (weird chocolate milk color oil, white smoke on startup, rough idle/running esp when hot). If it's not that, the you have gremlins. Definitely gremlins.

 

[Mitsubishified]

Coolant could be low, the thermomostat could be bad perhaps?

 

[phillabaum03]

Mine did that when the coolant was low.

 

[adidas_coin]

Only thing (non electrical) that would make a gauge go nuts like that would be air in the system (ie. low coolant. remember that there is 3 senders for temp. your cooling fans could be coming on at the right time using there sender. and the sender for the gauge could be at fault BTW the sender for the gauge is the spade connector.

 

[SaiyanFury]

Also make sure that your IC is getting the proper airflow. If your IC is not working well, you're sending hot air into an already hot engine.