I am trying to determine if I have a bad thermostat. I have let my car run for about 10 minutes. I turned the heater on, then the air conditioning during this time. The coolant never started flowing in the radiator. How long should it take for it to start flowing if the thermostat is good? Thanks in advance!

If you doubt the thermostat just replace it. If you want to check it, get an old pan and start boiling water. Use an old pan because of the ethylene glycol in the coolant. It should open at the rated temperature.

Domano,
Let your engine get to operating temp and feel the upper radiator hose. It should be warm and the coolant should be flowing through the hose. If your thermostat is bad, you will probably see your engine temp higher than normal if not overheating. Do you know what temp rating your thermostat is? You should be using around a 180. Hope this helps.

Make sure it isn't in upside down. The actuator side should be toward the block.