E&L AKM firing auto on semi

[Kastrioti]

Hi all, as the title suggests my E&L akm fires auto on semi sometimes. I've noticed that it usually starts off ok, but after a while there's a strong electrical burning smell followed by the gun firing on it's own on semi, and the grip gets really warm. I've been using a VPairsoft 7.4v LIPO, but it also does this with a 9.6V NiMh that I used just to check. I've had the gun for over a year now so it's likely out of warranty but it's been doing this for a while, I just couldn't be bothered to fix it/get it fixed as I was at uni. 

Does anyone know what the problem could be? I've messed a bit with motor height in the past and that's helped, but usually I have to lower it so much that the pistol grip becomes a bit wobbly. I am relatively inexperienced with AEGs so if this problem requires a tech can anyone suggest a good tech near west london? 

Thanks

 

[AK47frizzle]

Do you have a mosfet installed? Your trigger contacts are most likely burnt from not using a mosfet with a high power battery. So, it's becoming harder and harder to cycle the gun over time.

 

[Alicks]

....followed by the gun firing on it's own on semi, and the grip gets really warm...

When you say firing on its own do you mean without pulling the trigger?

have you had a mosfet installed in it? the death or the near death of the mosfet would explain it firing on its own without trigger activation

apart from that semi auto is governed by the cut off lever set up, so it could be worn, or the spring is out of place and reset is intermittent, or your having problems with your gearmesh on the selector switch or the selector switch being loose and riding upward into the full position

that wouldnt explain the heat from the motor or the electric smell tho as none of it is really in any sort of contact with the gear system 

motor height, worn shimming or lack of grease could explain the heat and the motor struggling

sorry cant be more helpful

Alicks

 

[Kastrioti]

Yeah so it just keeps firing on auto when I pull the trigger once and let go on semi is what I meant by that, same for when it's on auto. It doesn't do that consistently either as sometimes it will stop and only fire semi on semi, and auto on auto.

 

[Alicks]

You say it just keeps firing even after the trigger is released

that could be your trigger harness failing to reset, which is odd as you have a return spring on that to return it to start position once the trigger is released

semi problems are usually cut off lever wear or the selector lever problems with the gear mesh

but if the trigger is getting stuck in the harness/slot/rail then it could be a build up of dirt keeping it in position

however this should be knocked out of that position by the cut off lever

You should probably take it to a tech to have a look at tbh, unless you fancy peeking under the bonet yourself, if you do that then take it appart carefully and slowly,  take pictures, and if your really unsure open it inside a plastic bag so anything springing out will not get lost.

I cant recommend a tech unfortunately as i live in the northwest.

 

 

[Kastrioti]

Do you have a mosfet installed? Your trigger contacts are most likely burnt from not using a mosfet with a high power battery. So, it's becoming harder and harder to cycle the gun over time.

Somehow I missed this comment, I haven't installed one myself and as far as I can tell it doesn't come with one factory installed so I guess not. But it does come with a high torque motor so could I have messed it up by using a 7.4V instead of a 11.1V?

 

[Kastrioti]

Ok so just tested it on my 9.9V Life battery and there are absolutely no issues on full auto. If anything it sounds really healthy. However, as soon as I switch to semi it shoots very weirdly. I'll record it at some point but essentially if you hold the trigger down for just a bit too long on semi, it fires 2 or 3 times instead of once, but at a much slower fire rate than in full auto. It sounds really really bad and if you do this enough the motor heats up and you get that sort of solder smell going on. I'm gonna mess with the motor height and see if that's it, but unlikely to be that simple.

 

[Yukarin]

Sounds like the trigger contacts are on their way out.

 

[Kastrioti]

Might be a coincidence but after lowering the motor height things seem to be working. Are the trigger contacts in any way in contact with the shaft of the motor that could be causing them to be affected by it? Will torture test tomorrow.

 

[Iceni]

The only time I've ever seen a gun shoot on its own without a mosfet is with compromised insulation.

Chances are you have a bare wire on the + lead between the battery and the trigger, that is also contacting either the gun body or gearbox.

When the exposed wire touches the body/gearbox it bypasses the trigger and shoots full auto.

Your only solution from this situation is a re-wire, or patch repair on the problem wire.

 

It is also possible for a mosfet to die with an open circuit. In this instance, the gun would always shoot full auto as soon as you connected the battery.



If the problem only happens with a trigger pull then it's the contacts or COL.

It could be tight contacts, Faulty dolly, or pitting/corrosion. In all instances, it is normally far easier to replace the full contact system.

Sometimes if it's pitting/corrosion you can clean up the contacts, but you are not correcting the problem. Pitting is caused by arcing of the contacts and requires a mosfet or weaker battery be used.  Since you have to open the gearbox to correct it, Adding a mosfet even if it's a cheap Xcoretech Xet304u or acemos is recommended to stop the problem happening in the near future again. 

If it's the Dolly then new contacts are advisable so you get a good mate between the dolly and the carriage.

If it's tight contact points you can sometimes spread them out a little, This normally only happens after a rebuild. From wear, it's generally noticed that the contact points spread and fail to make a circuit.

It could also be a cut off lever issue. They can wear and fail to kick the dolly off the contacts. If this is the issue you normally need a new COL and matched contact set. This is a rarer problem but it does happen.



Your motor adjustments probably haven't corrected anything. Its rare motor height can affect the gearbox in regard to locking on auto, Unless in changing the height you have moved a wire that was holding the COL down, or moved the failed insulation so it is no longer contacting metal.



The best advice is to send it to a tech. Electrical problems can be difficult with airsoft guns if you don't know what to look for. Often an open gearbox will not show you the issues, and it requires someone who knows what to look for on the parts to see the problem at its root cause.

 

[Kastrioti]

Wow genuinely impressed with all the info and advice given. Since I know next to nothing about AEGs I might have a look inside but I'll likely end up sending it to a tech to have a look at it. 

Thanks everyone! ??