that was temperature sensor:

I have replaced it 3 times (all aftermarket $18.99, $26.99 and $7.99).
the ironic is that the one that finally worked was purchased on amazon for $7.95...
sold by Dade-US

https://www.amazon.com/gp/product/B01FU ... UTF8&psc=1

I got the sensor from auto supply store, need to ask them what brand that was.

Not sure how to answer the last question it is boiling over because fan will not go on at all, unless ECT is unplugged.

Replaced:
New thermostat
New ECT sensor

Water temperature gauge needle at 1/2 position (although suppose to be on red - new ECT and thermostat) since coolant is boiling, however fan does not go on. Turning AC on or off does not make any difference.

Unplugging ECT sensor turns the fan on. Plugging ...