Temperature gauge stops working occasionally

More then likely this is the coolant temperature sensor is beginning to fail. What happens is when this begins to fail it can act erratically or just stop reading all together.

I attached the process below on how to replace it which is what I would do in this situation.

However, if this is not happening all the time then you may want to wait until it acts up again to test it. When it does, we need to check the voltage on the sensor to find out if it is operating. I suspect you will find 0 volts which would indicate the sensor is not operating.

Let us know if you have questions on this. Thanks

Should I also replace the thermostat at the same time?

Only if you want to however, I see no reason to unless the vehicle is overheating. The heater not blowing on the one side, I don't think is related to the gauge.

So it is key to make sure the coolant is full and then change that sensor and retest everything. Normally these things are no a thermostat issue but if you are there and want to change now then that is not a bad thing.

Okay, I'll check everything out. Thanks again! Very helpful.

You are welcome. Please let us know how this turns out. Thanks