95 corvette over heats when sitting

The cooling fans are supposed to come on when the a/c is on. With the a/c off, the computer turns on the cooling fans when it sees the coolant temp getting around 220'. There is a sensor that reads coolant temperature that tells the computer what temp the coolant is. The sensor only works properly when it is in a liquid. If there is a bubble of air or steam at the sensor location, it will not read the coolant temp, or the sensor may be bad, or unplugged, or the cooling fan relay may be bad.

could it be the fan switch?

Heat control valve or temperature sensor are sticking. replace original parts.

If the fans come on with the A/c, it is not the fan switch. If you have dual fans, and both are on with the A/C it6 very well could be the sensor. Common problem. Also check for any breaks in the wires from the sensor or a lose connection.

Please note that the engine temp sensor and the radiator fan switch are separate items. When my trouble code indicated engine temp sensor, I replaced it and the system was still not cooling properly, so I had to replace the radiator fan switch also. Both units look like engine temp sensors and both monitor coolant temperature. The sensor is mounted in the block and the switch is mounted in the thermostat housing.