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CQR Self-Firing/Firing Without Trigger Pull

CQR Switch Gearbox Electrical Self-Firing Internal

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#1 BotdesignerXT

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Posted 06 April 2013 - 01:44 PM

I have a three month old (3000-3500 rounds lifetime) CQR Mod 1 which will fire/attempt to fire without the trigger being pulled.  As soon as the gun is put into semi or auto, i can hear and feel the motor trying to pull the spring.  After releasing the trigger, the gun continues to fire a few rounds before failing to pull the spring, but struggling to do so.  Occasionally, the gun will even succeed in firing without ever pulling the trigger!

I attribute it to some sort of switch failure or wire shortage, and while I am comfortable working with the internals of the gun, I would like to know if anyone has come across this problem before, and if so, how did you fix it.

Thanks

#2 niko_gpsy

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Posted 06 April 2013 - 03:50 PM

If the gun has never been disassembled it can be a strip or pinch somewhere in the wiring. It could possible occur during closing the split receivers. Another possibility can be a bad battery connector. Examine the pins in the tamiya plugs and make sure the female and male pins are making proper contact when connected. Also check that the wires to the plugs are not coming loose.
If the problem isn't any of the above it can be a bad selector plate, cut off lever or possible a bad trigger switch assembly.

#3 BotdesignerXT

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Posted 06 April 2013 - 04:14 PM

I am aware that the cable leading into the hand-guard is crimped a bit, but i checked and it seems to have great connectivity.  All the other external connections are good as well.  I am almost positive that it is internal.  But just for curiosity, you said that a bad contact at the tamiya connectors could also cause this same problem.  Pardon my ignorance, but how if it is before the trigger switch.

#4 niko_gpsy

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Posted 06 April 2013 - 04:17 PM

If the connectors do not make a clean secure contact, it can arc which can also result in the same symptoms as a pinched it stripped wiring.

#5 BotdesignerXT

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Posted 15 April 2013 - 04:29 AM

Okay, so i finally got around to taking apart the gearbox to look around.  First, the cut off lever was fine with almost unnoticeable wear. However, the trigger switch had burn/arc marks (Is this normal).  Another thing i noticed was that the spring that pulls the switch off the contacts was a bit weak, and it got stuck a few times.

To eliminate a few possibilities, I confirmed that the electrical safety did indeed stop the motor from getting power when self-firing.  Also, since it is the positive lead that completes the circuit, the unwanted connection is happening between the safety and the positive motor lead.  That being said, i am quite sure the problem was the switch.

#6 niko_gpsy

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Posted 15 April 2013 - 07:57 AM

ALL trigger switch contacts will arc to a degree no matter what type of battery you use.  So that is the reason we always recommend that you use batteries within the the spec specified which is about 18 to 20amps.  
If your contacts are sticking you can coat it with a dielectric grease which will not only lubricate the contacts but also protect it from arcing/ or when it arcs.  I use "Super Lube" for this reason.

#7 BotdesignerXT

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Posted 17 April 2013 - 05:38 PM

I put the gun together and it worked... sort of...

When in semi and auto, the motor stays off like it should and only fires when the trigger is pulled. The trigger switch doesn't stick either.  However, i think i screwed something up so that when the gun is put in safety, it tries to shoot.  The electrical safety somehow is completing the circuit when in safety.

Edited by BotdesignerXT, 17 April 2013 - 05:40 PM.


#8 niko_gpsy

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Posted 19 April 2013 - 06:18 AM

View PostBotdesignerXT, on 17 April 2013 - 05:38 PM, said:

I put the gun together and it worked... sort of...

When in semi and auto, the motor stays off like it should and only fires when the trigger is pulled. The trigger switch doesn't stick either.  However, i think i screwed something up so that when the gun is put in safety, it tries to shoot.  The electrical safety somehow is completing the circuit when in safety.
Have you checked the copper plating on the selector plate to see if it has come loose and is making contact with the trigger switch assembly when safety is engaged?

#9 BotdesignerXT

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Posted 11 May 2013 - 05:10 PM

I finally got the gun working again.  :thumbsup: The last problem was just my negligence n that i bent one of the wires in the gearbox, causing the firing.  Just wish it didn't take so long to find out. :P

#10 gcw360

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Posted 11 May 2013 - 08:32 PM

View PostBotdesignerXT, on 11 May 2013 - 05:10 PM, said:

I finally got the gun working again.  :thumbsup: The last problem was just my negligence n that i bent one of the wires in the gearbox, causing the firing.  Just wish it didn't take so long to find out. :P
The good news it that YOU FIGURED IT OUT!!!! Congratulations.





Also tagged with one or more of these keywords: CQR, Switch, Gearbox, Electrical, Self-Firing, Internal

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