AEG Not Cycling Need Some Help

[Noob7_0]

Gun Doctors and AEG Gurus,

My G&P M4 has stopped cycling. I purchased it second hand off of the Classifieds. It has the following:
-Trigger Master SMU mosfet
-Systema High Torque complete gearbox
-Guarder Infinite Torque up motor
-Front wired to deans, but has an adapter for small tamiya runs with a 11.1v Lipo

I took it for a spin a week ago and after about 800 rnds it stopped working. I was shooting one minute, went safe when the round ended and when the next game started it wouldn’t cycle. It is rigged to only fire in semi. The previous owner claims it was inspected by a gun doc and ran fine before I bought it (which it did for about 8-10 mags).

I have very little experience with AEGs and I don’t know where to start with the trouble shooting. I am planning to send it to the Doctor’s office but I was hoping to get some insight on what the problem might be. I have yet to open the mech box. I have tried firing it with a 9.6v NiMH and had no luck. I tried a different motor with the 9.6v NiMH and had no luck. The fuse appears to be intact and to the best of my knowledge the MOSFET is ok too.

My initial thought was the 11.1v Lipo fried something or maybe something got screwed up int eh mech box. I will open it tomorrow night if I have time so see whats what.

Any help/gun doc recommendation would be appreciated.

[HKGhost]

What is happening when you pull the trigger? A little bit more details would make it more easier to diagnose the issue.

[bizkilter]

if your battery is near dead it might seize the piston..

[Noob7_0]

The trigger pulls part way as normal and at the point where it would fire there is some resistance and then it keeps compressing to it's stops. There is no grinding sound and the
Motor doesn't spin.

The batteries are charged and the piston is in it's forward position.

[HKGhost]

So let me get this right. The gun doesn't complete a full cycle but rather pulls the piston back but doesn't fire? Or the trigger is pulled but it doesn't make contact? I'm trying to make sense of this "there is some resistance and then it keeps compressing to it's stops". If you pull the trigger and nothing happens, even when the motor is out of the gun, then it could be that your switch assembly contacts is fried and has a built up of carbon.

[Noob7_0]

Sorry for the poor descriptions. When my other AEG's trigger is pulled it is smooth an fluid. When my problematic trigger is pulled half way, it catches on something (resistance) there is a sound as if it has broken away from what ever was obstructing it and then the trigger pull is completed smoothly. The piston never moves.

I will open the mech box tonight and check the contacts and look at the gears.

Thanks for you effort in truly to help Ghost.

[Noob7_0]

Opened the mech box. One of the contacts on the switch assembly has melted/corroded. A small piece of the switch housing is broken which has caused the switch to come out of alignment. I can only assume that this broken piece was causing the weird trigger pull.



I am planning to order a new switch assembly and see if that fixes the problem.

[cadpat_tact]

Originally Posted by Noob7_0

I am planning to order a new switch assembly and see if that fixes the problem.

I'm in the same boat, only with one of my ICS M4's. The trigger action was not smooth and it required more pressure than normal to cycle. Upon disassembling my gun I noticed the switch assembly needs to be replaced. Note the buildup of carbon and the cracked contact. Click to see it super close-up:

_DSC2736b.jpg

[Kos-Mos]

Originally Posted by Noob7_0

Sorry for the poor descriptions. When my other AEG's trigger is pulled it is smooth an fluid. When my problematic trigger is pulled half way, it catches on something (resistance) there is a sound as if it has broken away from what ever was obstructing it and then the trigger pull is completed smoothly. The piston never moves.

I will open the mech box tonight and check the contacts and look at the gears.

Thanks for you effort in truly to help Ghost.

Your gun was probably just in semi lock.

To fix that, you only needed to remove the mechbox from the gun and either pull the ARL (anti-reversal latch) to let the piston move (it was about 1/4 way back) or short the two solder points on the trigger unit (push the selector plate in auto and use a paper clip to tap the two contacts).

The problem is that the cut-off lever was disconnecting the trigger block right before it was making contact.