99 Jetta problem with coolant sensor

Sometimes my sensor work. I've clean the connection to the connector & sensor. When the sensor doenst work..i dont get a check engine light at all..(How come?) Also what is the other sensor thats located on radiator hose..it is a 2 connector type towards the front of the car?

I believe you have the 4 wire sensor (in the flange at the head). It has two sensors, one for the gauge & one for the engine computer. If the gauge side goes bad it won't set a light.

Even if I disconnect both sensor I still dont get a engine light. I think the problem may be the connection where the ground is. The reason I say is because I have problems with my gas door ejecting sometimes and also the trunk light with work sometimes and it all seems to lead to the dash wiring harness. What do ya think?

I'd say they're seperate problems. I don't know how long it would take for the light to come on after disconnecting the temp tensor. It may be storing the code, but not turning on the light yet. I assume the light comes on for the self check on startup.