Due to heat from the bulb, the housings warp. The housing is 3 pieces. The cover, the upper section with bulb socket, and lower section that attaches to the hatshelf. Remove the cover. At the bottom of the housing there is a tab which releases the upper section of the housing. Lift the tab and slide the upper section foreward to release. Once removed, you will find metal contact tabs that complete the circuit between the housing halves. These tabs are often deformed from heat and/or corroded. Bend the tabs up on the lower half and down on the upper half, then sand them clean. This should get your lamp working again.