My 2002 chevy tahoe temp gauge keeps going up and down

I think your issue is with your fan(s), its an intermittent problem with the sensor that sends a signal to turn the fan on and off.

Someone mentioned that also. Im trying to save money by fixing myself. I have no idea were that sensor is located. And how do I find out if it is bad.

Have your system checked. You may have air in the system or are low on freon. If you not all that familiar what the system, it is best to have it checked by a refrigeration person.