rear view mirror sensors

[movado750]

My sensors for the rear defroster will not come on. Any ideas. Light comes on but nothing defrosts on the rear windows.

 

[exp500]

Check voltage thru light at headliner.

 

[Tbruz]

Barn doors or lift gate?
On my 97 with barn doors there are two spring loaded plunger type connectors at the upper side of each door that make contact with the body side; completing the circuit. These are notorious for corrosion and can easily be measured with your volt meter and cleaned as required. Protect the cleaned contacts with some dielectric grease once cleaned off.
I'm sure the lift gate has similar connectors; I just have no first hand experience with that configuration
Tbruz