'90 Camry fans won't turn on/overheating

Hello all. I have a 1990 Camry whose radiator fans won't turn on. I've already checked the fuses and relays. I initially changed a 10A fuse and replaced it with a 15A fuse yesterday and the fans turned on after the car was basically overheating. However, when I tried the car again today, the fans didn't turn on at all. No fuses were popped & I removed the thermostat to see if that might do anything with no results. I'm thinking it might be the temp sensors attached to the fans but I can't find where they are. I searched all on-line with no luck. Can somebody please tell me where they are located? I feel really dumb asking this but I have no idea where to look or if these cars even have anything like this in them. Am I on the right track with what I'm thinking? Anybody who has any idea on this, your help would be greatly appreciated.
By the way, I don't know if this help or not, or if its supposed to be this way, but the coolant does'nt auomaticaaly circulate when the car turns on. As a matter of fact, the engine has to get pretty hot before it'll start circulating. This is with the thermostat out of the car. Any thoughts? Thanks in advance for your help.

The sensor for the radiator fans is near the thermostat housing. The coolant naturally will stay cool for a long time because the thermostat has been removed; and now the coolant will continuously circulate through the radiator to be cooled instead of going back to the engine till the coolant is hot enough to make the thermostat open and send coolant to the radiator.