THERMOSTAT

Friend, it seems we're speaking different languages, haha. There's no sensor that circulates the water; the pump is what circulates it. There's no sensor for that. Or are you referring to the fact that the electric fan isn't turning on?

If you removed the heater passage and put plugs in its place, that's the problem, my friend.

How did you verify that the water isn't circulating? Try this: remove the thermostat valve or spring, close everything again, refill the system with water, and then manually pinch the hose that goes into the top of the radiator at 1500-2000 rpm (with hot water). See if there's really no water exchange. If you don't feel any water flow, you need to check the water pump again. Sometimes everything seems fine, but the impeller on the pump can come loose.

All tests were done and nothing. The vehicle is a 1997 BMW, it's fully electronic, full of sensors, and has four computers. The vehicle is running, except the water won't circulate. The pump is good, the heater isn't working, and it doesn't have a cap.

It's difficult for a duct to get clogged. Look, do a simple test: remove the thermostat as Bata says, and then remove the upper radiator hose and the lower one. Pour water through the lower hose and it should drip out. If this works, but there's no circulation when you reassemble it, then the compression in the combustion chamber is clogging the system. I've only seen this once in my life, but maybe that's your case.