Autometer Boost/Vac Gauge not lighting up at night ?

Hey folks so my Autometer Boost/Vac Gauge is not lighting up at night sometimes randomly. When I start the car sometimes it does not come on sometimes it does, sometimes when I turn on my headlight it could come on sometimes it doesn't. When it does not come on I flick on and off my headlight until it comes on, sometimes it randomly turns off at night in the middle of driving. Anyone have any idea to trouble shoot it.
Here is a pic of it working just fine below.

<a href="http://imgur.com/ZeAw4sQ"><img src="http://i.imgur.com/ZeAw4sQ.jpg" title="Hosted by imgur.com" /></a>
 
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