I have trouble getting the bubbling tube to bubble. Does the glass tube go with the flat side on top of the bulb or the pointer end of the bulb?
Thank You
Ken M
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The flat side goes on the bulb. You also have to be patient, it can take a few minutes. I've seen folks use some conductive grease to help the heat flow to the bubble tube.
Thank you, what kind of conductive grease since it will be right against the bulb. In the beginning the bubbles started in a couple of minutes, but now it takes ten minutes running at 14v.
Ken M
What I saw was some sort of heat conducting epoxy, I believe it was initially for bonding heatsinks.
I had one of the oil derricks, I just waited until it got going. The tubes do gradually lose their "bubble", so at some point, you might need a replacement. They're just like old Christmas bubble-lights, those die after a certain amount of use as well.
Did you try giving them a tap with your finger after they warm up.
Works for bubble lights! 
