Snap-On MT-335 Coil Tester...question

d.j. moordigian

d.j. moordigian

Well-known member
I inherited a Snap-On coil tester, # MT-335. The 2 secondary studs at
the top on the box(for coil output), have a spring on each of them.
Something fits between them....but I don't have a clue. Anybody out
there have one of these tools or knows what goes there?
Thanks, Dudley
 
There should be a glass tube between the springs.
I live in Clovis call 291-0320 if you need any more information.

George Day
 
Like George said there should be a glass neon tube in there. Mine broke and I don't
know were to find another one.

Bob
 

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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.
 
A FB member named (I think) 500KR collects owners manuals for all kinds of tools and such. He might be able to help you with the Instructions.
 
Gent's

Thank you for the help! George Day, #2 post, said his tube "glows", so I'm
thinking that it's a neon tube of sorts. I have no idea what it does( filter or load?)
for the secondary,...I really don't do electricity. I will try the Snap-On sight
............. http://www.vintagesnapon.com/forum/index.php:)................
when I / if figure it out, I will post the find.
 
1. I called Snap-On,....no help.
2. I haven't used the web sight,..but I did look..I didn't find it easy
too navigate, maybe you have too join.
3. But I did get this far, it is a " neon pilot light ", when it gets warm/hot.
I would think the voltage would have too be very high, say maybe 25,000 volts?

I like tools that are complete, I'm sure they put that there for a reason, right?
 
For your Snap-On tester I can email you a copy of the instructions. The tubes are called Geisler tubes and seemed to be used in all the old distributor testers such as Sun(now Snap-On owned) Allen, Weidenhoff and others. Snap-On used to sell a small ball point pen styled tester to check spark at plugs. It also used a Geisler tube. My email is sponge19501924@yahoo. Of course no charge for info.
 
KR500
Thank you for the information! For some reason, your email is not working
when I tried running it. If you click on my name, you can send me an email
of the instructions. Thanks again.
 
Dudley,

Maybe the neon bulb is used to determine the polarity of the spark from the coil during testing.

See this video on U Tube:

http://www.youtube.com/watch?v=OKPPbLXNOt0

The neon glows around the left "pin" of the bulb with a negative voltage applied and the other "pin" if a positive voltage is applied.

I remember seeing neon bulbs hooked to AC in old radios with vacumn tubes that glowed around both "pins" as AC current changes polarity 60 times a second so it appears that both "pins" are lit at the same time ...

Most pilot neon lights on radios ran on about 100 volts.

Notice that the fellow in video used eight 9 volt batteries or about 72 volts for his experiments.
 
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