When my car is at idle the thermostat will rise almost to the middle. However, while driving the car (usually on the freeway) the car registers as being cold. I just recently replaced the thermostat so I was wondering if it may be something else?

 

Likely your coolant temp sensor. It's a common failure point on these cars. It's about $20 or so and a fairly easy DIY replacement. You can order it at www.ECSTuning.com or www.PureMS.com. Call them up with your VIN number handy so they can get you the right one (there are three types).

 

hello, i have a similar problem with my audi a4 1.8t q2000yr.
when i both the car coolant temp gauge pointed in a mid from cold and norm temp. when i changed the thermostat the gauge was showing a normal temp for a wile, but now sometimes the temp is in the midle and when you drive for a wile the temp drops to the cold.
i conected the car to the vag com. and it shows that when the gauge showing me that the engine is cold vag com shows that engine temp is normal ~90C
is there more than one coolant sensor or it's instrument clusters problem?