1998 Ford Escort gets hot

I have a 1998 ford escort with 165,000 miles on it, recently I stopped to help push a car out of traffic. When I returned to my car (I had cut the engine off) the needle was up near "H". I took it to the shop and they replaced the thermostat, it drove fine for about a week then on my way to work the needle suddenly shot up to "H" again, I turned around and drove it straight to the shop and this time they replaced the water pump. It drove fine today, but after I pulled into a spot in the parking lot at work, I turned the motor off and turned the key back on to listen to the radio and watched as the needle rose back up toward "H" again. Is this normal? Also My electric fan does run with the key turned on, but will not run with the key turned off, I thought that ran regardless if the car was on or off? I've put about $500.00 into this car over the last few weeks, I drive 82 miles to work (that's 164 miles a day). Any ideas?

Mike