94 camry 4 cyl LE - Cooling problem.. Fans don't run when engine is hot

Hi,

I have 1994 Toyota Camry LE, 4cyl

Since past 10 days, always my temperature sensor on Dashboard shows "High"

I did following

1. Checked the coolant levels (level is full in recovery tank)
2. Radiator upper and lower hoses has different temperature (Upper one is hot and lower one is cold)
3. When temperature sensor shows "Hot"... Fans were not running
4. When engine was very cold and started the engine, Fans were running first

So with above symptoms, what would be the problem for Cooling failure ??

a) Is it Thermostat problem ?? Is it easy to replace (DIY ??) b) Where is the Fans Fuse (in case, if it needs to be changed) ??

Regards, Rama