Trunk closing?

I just had a strange occurance, and not having the service manual yet, could anyone shed some light on this? My trunk showed that it was open on the MFA, and it was closed. I stopped and opened the trunk and checked for any obstructions, found none, and reclosed to no avail. Did this several times and finally it showed that it was closed. My main question is where is the sensor to show that the trunk is closed? I moved the little door that covers the body side latch and it did nothing, and could not find any switches. Could it be a mercury switch in the left side hinge? Thanks for any help, the problem cleared itself, but in the future if it returns, I'll know where to look.

Did you just get finished taking the car thru a carwash? The reason I ask is everytime I take my New Beetle thru a carwash the light for the rear hatch comes on even though the hatch is closed.

No, the car was dry, mid afternoon, temperature about 70. Do you know where the switch is on the Beetle?

I'm thinking the switch is located near the latch.