April Fools Day... But This is No Joke!

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As a result of running halogen headlight bulbs via the ammeter needle reacted in a big way and jammed on the discharge side.  I have since wired in a pair of relays.  Then – as I’ve done before – I tapped the back of the ammeter with something solid hoping to free the needle.  What I think I seem to have done, though, is cause a short and burned out the ammeter!!!   When I took it apart I could see that the “coil” has come in contact with the face and a major short has occurred.  It could easily have caused a fire!  The other damaged ammeter I have shows exactly the same symptoms.  If you look closely you can see where a section of each coil has burned away.  So the question is:  did something cause the coil to overheat/cook and expand, thus touching the face, or was it just my tap on the back of the instrument that did it?  Looking at the way they’re made I can see the clearance between face and coil is tiny.  I now have two damaged ammeters and I need to know what’s happened.

 

I’d appreciate the group’s thoughts

 

I’m also once more in the market for a spare ammeter – help!

 

Cheers….. Peter