temperature gauge not working

Hello,

It sounds like one of two things maybe happening. Fist is the temperature gauge is working fine and it is a thermostat that is stuck open causing the engine to run cold or you have a temperature sensor that has gone out.

Here are guides to help us confirm the problem and get it fixed.

https://www.2carpros.com/articles/replace-thermostat

and

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

Here are how the jobs are done on your car (below)

Check out the diagrams (Below)

Please let us know what you find. We are interested to see what it is.

Cheers, Ken

Heater problem
2005 Pontiac Grand Prix 6 cyl Front Wheel Drive Automatic 87000 miles

When sitting and warming up the car will not warm up inside. When driving it will start to warm up. The temp gauge gets a little bit above half way but doesn't go any hotter, when driving the gauge goes back down and the heater starts to work. No smell of antifreeze or anything and it may just be ironic (have no idea) but the seat warmers won't work either.

You may have air in the system or the heater core could be plugged up from Dexcool gone bad.

I would flush the whole system and install a new thermostat. Pull the hoses off the heater core and flush that in both directions thoroughly with a garden hose under pressure.