Amp meter jumps back and fourth

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Model T Ford Forum: Forum 2015: Amp meter jumps back and fourth
Top of pagePrevious messageNext messageBottom of page Link to this message  By Ed Saniewski Denville NJ on Wednesday, January 07, 2015 - 09:22 pm:

I got the spare motor into the canopy express and fired it up. When I bring the idle up, the amp meter starts to jump from 10 amps charge to 10 amps discharge every other second. Is there a problem with the cut out? Any ideas on trouble shooting this problem. Thanks


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Wednesday, January 07, 2015 - 09:35 pm:

Put a test lamp on the batt terminal on the cutout with it running.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Jablonski on Thursday, January 08, 2015 - 05:50 am:

Check the point gap on your coils.... one may not have enough clearance. Observed on older coil rebuilds, the cushion spring rivit has worn into the cushion spring making a larger opening resulting in the rivit limit useless and the points in constant contact.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Thursday, January 08, 2015 - 10:59 am:

Ed,

Before you bring your idle speed up does the ammeter show only discharge? I think what you're describing is somewhat common. The fluttering needle is caused by the points in your cutout alternately opening & closing as the generator output is just hovering at the point of keeping the cutout points fully closed. Increasing the rpms a bit should result in increased generator output, closed cutout points and a constant charge indication on your ammeter. This all assumes you're using a stock Model T cutout and not a regulator or diode type.

Another possibility may be if you are running an electric fuel pump. They can place an intermittent load on the circuit and cause ammeter flutter. Of course there's also the weird stuff like intermittent short circuits or maybe a bad spot in you generator armature, or poor commutation in your generator.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Zahorik on Thursday, January 08, 2015 - 11:17 am:

What's the condition of your generator? If the brush rigging insulator is in bad shape or if the output wire insulation is broken, you could be suffering an intermittent short. This would ground the generator and reduce the output to zero. You mentioned 10 amperes as a high point. That would suggest that your third brush is not at the optimal position. That could be another indication that generator condition is suspect. Good luck Mike


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