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Unintended Firing

1742 Views 19 Replies 6 Participants Last post by  OutlawAirsoft
Hey all,
I am installing a very simple 3034 mosfet in an ar47 I recently purchased and am having an interesting issue. The 'fet works fine, but with everything put together, when I switch from semi auto to full auto it starts cycling. It only cycles about a quarter of the way, but it is anoying and sometimes that causes it to fire. I have looked inside the gearbox but don't see anything obviously wrong. I suspect the cutoff lever is bumping the trigger trolley enough to complete the circuit, but I can't tell for sure. It also occasionally fires full auto in semi auto mode.
Any advice would be greatly appreciated.
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Does the selector plate have a metal plate on it? Some companies use that design to break the circuit when in placed in safe.
It’s also is known to short if parts get bumped around a little too much.
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Yes it does. It does seem as if it is shorting through this, but I can't see how. Should I remove the plate? I could rig something up to bypass the plate, but would this be feasible?

I did some diagnosing earlier today and found that it only misbehaves when the grip screws are tightened all the way. If I leave them backed off a little bit (enough to keep the grip firm, but not reefed on), it does not misfire. But when I was using it, apparently my holding it produces the same effect that tightening the grip screws does, and it fires again abnormally.
As others have said since it misfires when you adjust the grip screws it's more than likely a short there.

I would so check the wiring around the grip to make sure it's not getting worn down by the pinion gear or has any breaks in the insulation from removing the motor.
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I highly suggest pulling out the wiring harness and checking it for exposed wiring or small cracks in the insulation.

I would also apply more shrink tubing to the motor connectors like others have said, it sounds like that area is lending a fair share to the problem.
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