Constant full auto when battery plugged in

[billythefish]

Lets start with the problem.
As soon as i connect my battery to my rifle, even on safe without holding the trigger, the gun just constantly keeps firing in full auto until i remove the battery.

How i think it occured.
I put a new (too powerful) spring in that gave my AEG 430fps. However it kept locking up in the rear position and eventually the battery went flat. When i went to replace the battery from the stock i noticed it was redders and a small amount of smoke was coming from my stock. Needless to say i stoped my days play.

Ive put in the stock spring again but could my problem be the switch lever or a fuse of some sort? None of the wires look burnt or melted. My rifle is a second hand SRC m4 with a systema piston head. Surely if my fuse or resistor has gone (i don't even know if i have 1 although there is a little black box spliced into the cables in the stock) there shouldn't be any charge running to the motor at all? Also this little black box gets extremely hot extremely fast.

Any help would be apperciated but im not very electrically minded.

[baddbaz]

Re: Constant full auto when battery plugged in

Sounds like a switch or the wiring has fused/ melted itself together mate !! Need to get a multimeter or another way of testing your circuit in the gun .. Could be trigger contacts as well

[loki7491]

Re: Constant full auto when battery plugged in

I had a similar issue with an M4 i messed about with. Semi-auto only for me though.

In putting it back together i had pinched wires in the stock tube and about the gearbox causing short circuits everywhere!

Take it apart again. Check all the insulation on the wires and tape up as required. CAREFULLY re-assemble. That solved it for me.

[baddbaz]

Re: Constant full auto when battery plugged in

Just do not use a lipo to test it with . Much safer to test with a nimh battery.....

[jonny lovegrove]

You were going semi at that fps i hope! Sounds like trigger contacts have broken. Gearbox opening time!

[billythefish]

Re: Constant full auto when battery plugged in

I never thought i get replies so quickly!

Unfortunately i had to go full auto at that fps as it would jam for 5min and the only way it would come unstuck was to keep pressing the trigger on full auto.

Baddbaz i only use nimh. Lipos are way over my head.

Ill try and get some photos on of the part i think is faulty

[billythefish]

Re: Constant full auto when battery plugged in

Well ive established its not the trigger contacts

[baddbaz]

Re: Constant full auto when battery plugged in

Wondering what the box you are on about actually is ???? Fuse box ? MOSFET ( plug an play type ) ? Can you put up a pic mate ? Might help

[r6shooter]

Re: Constant full auto when battery plugged in

Tigger return spring mate most likely bet

Also check the contacts on the selector plate

[simon]

Re: Constant full auto when battery plugged in

Had same problem, simple fix if its the same. Take the gearbox out of the lower, no need to open the gear box. Look on the left side where the selector plate sits, are the two metal contacts touching the gearbox frame? Mine had straightened and were making a constant contact. If yes, bend them back so there not touching and fit a small bit of rubber to the ends so they dont touch again. Worth a try before opening the gearbox.

[billythefish]

Re: Constant full auto when battery plugged in

Right update

Ive had the gearbox out from the lower reciver so there wouldn't be a short circuit between the selector plate and the body. Plug the battery in and the problem still exists.

I took the gear box apart inspected the wiring and trigger contacts. Nothing appers to be wrong. While the gear box was open i pluged the battery in (no spring in of course) and the problem still exists. I tried wedging bits of carboard into all the switch parts of the circuit to break the contacts. So theoretically there should be no power getting to the motor (correct me if im wrong) and still the motor wirred round constantly.

So this brings me back to this little black box that appered to be smoking and gets unuasually hot. Im trying to get pictures up but im not computer wizz so hold tight.

All i can say about the box is that the negative lead(black) on the battery leads into the box, where it then splits down into 2 wires 1 thicker than the other. The thick 1 thats the same size as the posotive lead go to the motor. The thin one goes to the trigger. While the posotive lead also goes to the trigger then the motor.
I wish i new what this box was it would help us all.

Thanks for all your help so far

[BioSniper]

Re: Constant full auto when battery plugged in

Sounds possibly like a mosfet?
Below are the other most likely options:



Fuse holder + wires (imagine a gearbox there, the fuse holder in this case is white/clear)


Trigger block, just below the tappet, to the right of the sector gear and above the trigger itself (the white/clear bit) sits inside the gearbox.


in-line "mosfet" (I use the term loosely)


A "normal" mosfet. This usually has 2 wires on one side, 3 on the other..
^ This is the one that I think you mean.. maybe not these colours exactly, but the description kinda fits.

Any of those familiar?

[billythefish]

Re: Constant full auto when battery plugged in

A normal mosfet. Looks just like it. But the insulation is split and it looks like its had some sort of heat damage. Could a short circuit at the normal mosfet cause the constant firing as soon as the battery makes contact.

As i don't know what a mosfet is or what it does i don't know.

[baddbaz]

Re: Constant full auto when battery plugged in

The answer is yes ime afraid

[seansamurai1]

Re: Constant full auto when battery plugged in

That would explain the 5 minutes before it would work again, thats the thermal fuse.

Sounds like either A you have blown the mosfet or B the contacts are fused together.
If its the latter then the mosfet might have been the cause of that.