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Old 01-11-2013, 09:02 AM   #7
Kevin in NJ
Senior Member
 
Join Date: May 2010
Location: South East NJ
Posts: 3,398
Default Re: Snap-On MT-335 Coil Tester...question

I have one of those testers as well as others like it.

I would not worry about the tube. It appears to be a sealed glass tube with who know what in between. The ends are coated with some kind of metal. I am wondering if it is just a way to indicate there is high voltage when you have the gap too far apart to have an arc.

These are really pretty simple and effective testers. You just see how far an arc you can sustain when coil is cold and then heat it up and see if the arc severely reduces in length.
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