any make after 1997 will be susceptible to electrical issues when engine is normal. i wish they would have left the computer stuff out of vehicles.
gauge is most likely electrically impaired.
your coolant level could be low
i just put in a new radiator and now temperature gauge reads high but their are no leaks
Low Coolant or faulty gauge
If the coolant gauge reads 100°C (212°F), it indicates that the engine is overheating. This can lead to severe engine damage if not addressed promptly. It's essential to pull over safely, turn off the engine, and allow it to cool down before checking the coolant level or seeking professional assistance. Continuing to drive under these conditions can result in a blown head gasket or other costly repairs.
If the temp gauge reads normal and the engine is not overheating, the thermostat is doing its job. The thermostat maintains the coolant temp by opening and closing allowing the coolant to flow or not to flow. When it is closed the coolant doesn't circulate.
Either your engine coolant temperature is HIGH , your oil pressure is LOW , or your fuel gauge reads at or near empty
If it's a VW, it's the water pump. For the temp gauge to read properly, it must have LIQUID coolant flowing over it. Steam will not provide a proper reading. If there's a coolant leak, it could produce a fluctuating reading. If you're losing coolant but not finding coolant puddling under your car, then the leak is not just a hose or line. It could be a manifold gasket or something. That ain't good. I recently ditched an old car because of that exact problem.
Usually there will be a repeating chirping noise during engine running, also your tempurture gauge reads hot . with me, i was leaking antifreeze/coolant, but not all the time
If the engine is not overheating and the temp gauge reads normal, the thermostat is doing its job. If the engine is overheating, the thermostat may be stuck and in need of replacement.
check/replace the engine coolant level sensor located in the engine coolant overflow reservior (located at the rear of the engine compartment pass. side)
Connect a gauge and freon can to the AC low side port of the A4. With the engine running and AC on high, open the freon valve and allow coolant to flow into the system. Turn it off when the gauge reads full.
Very possible your temperature sending switch is bad. If both fans work with AC, then it's also possible you have a wiring issue.