Temperature.
Could be low on coolant or a sticky thermostat.
low coolant
When you turn a corner the guage fluctuates.
Possibly the thermostat is opening and closing with the water pressure changes. Could be low on coolant also.
A short in the turn signal wiring can cause the voltage gauge to fluctuate. A loose ground wire can also cause the gauge to fluctuate.
Either bad ground on your gauge or your electric cooling fans are going bad.
is the coolant disapeering at all ?
In cold weather, the temperature gauge may fluctuate as the thermostat regulates the temperature by turning the heat on and off to maintain the desired level of warmth in the house. This cycling on and off is a normal part of the heating system's operation to keep the indoor temperature consistent.
The low coolant warning light is just to the left of the bottom of your engine oil pressure gauge
An automobile temperature gauge can fluctuate when the thermostat is opening and closing erratically. The temperature gauge can also fluctuate when the ground wire is loose.
Could be the coolant temperature sensor.
Possible causes of gauge not working. Faulty gauge Blown fuse. Open circuit in wiring to the gauge. Temprature transmitter in engine faulty. ( most probably the actual fault ) Lack of coolant in the engine.