View Full Version : Fuse

01-16-2005, 11:20 PM
I blew my fuse on my Mp5 A4 (TM), and the fuse said that it was a 15 amp fuse, yet when I got another 15 amp fuse from the local gas station it immedietly blew out. Anyone know what the problem could be? The bat is an 8.4 1700 mah.



01-17-2005, 12:53 AM
What has been done to the gun lately?

Fuses blowing are typically a sign of an internal problem, such as a part breaking or gears being shimmed improperly.

We need more info on the gun's history to offer more help.

01-17-2005, 08:22 AM
I removed the engine because I thought I has stripped my gears, and when I put it back in the fuse was blown. When I got the other fuse it immedietly blew (right when bat was plugged in) The gun has no upgrade work done.

01-17-2005, 09:10 AM
Ok, one very possible problem is that when you put the motor back into the pistol grip, the motor wires were not routed correctly. Thus, the motor got jammed into place and is jammed against the gears inside. Unable to turn, it blows fuses.

Take the motor plate off the bottom of the pistol grip again. Can you push down on the motor and it springs back up (moves freely up and down)? If it will not move freely, you need to pull the motor out, route the wires along the bottom of the grip and then up the side of the grip, and then put the motor in. There is a large spring on the shaft of the motor that causes it to spring back up. If the wires are routed correctly, they will not cause the motor to get caught on them, and the motor will ride up and down when you push on it and then release.

Give that a try first.

01-17-2005, 10:21 AM
The motor moves freely, and seems not to be stuck, the fuse just blows immedietly when I plug in the bat.

01-17-2005, 10:54 AM
Take the motor out, and then hook the motor wires up to it. Plug the battery in and pull the trigger. Does the motor run?

01-17-2005, 12:02 PM
Motor runs now. Fuse problem fixed, yet now when I insert the motor into the grip and replace the motor plate, I could hear the engine spinning. It seems it is not being forced to touch with the gears. Another, minor, problem is that every few shots the wires that connect to the motor pop off.

01-17-2005, 12:12 PM
Are you referring to the motor or the mechbox as the "engine"? If the little electric motor works and you can just hear it spinning in there, the pinion gear or the bevel gear might be stripped. Look at the pinion gear (gear on the electric motor). If it is fine, shine a flashlight down into the pistol grip and look at the first gear you see (bevel gear) to see if it is stripped (teeth damaged/missing).

If both of those are ok, are you saying that you hear spinning sounds (as in the gears spinning) from the mechbox? If so, your piston could have been stripped, so the gears are spinning, but there are no teeth on the piston to catch, so the gears just spin freely.

To fix the motor connectors, carefully squeeze the part that slides onto the motor tabs so that they are tighter, and then install them.

01-17-2005, 12:19 PM
Both the gears are fine, nothing is stripped and I am almost positive the piston is O.K. When I push the engine down and pull the trigger it shoots fine, yet when I replace the engine plate, it seems the engine is not touching the bevel gear. I was wondering if I could fix this by taking the spring that attaches to the shaft of the engine, and putting it between the engine plate and the engine itself, so that it pushes the engine into the little hole and to the bevel gear.

01-17-2005, 12:21 PM
No, leave the spring where it is. Did you take the set screw out of the motor plate that is in the middle of the plate? That set screw pushes on a small metal disc that sits on the end of the motor, and serves to push the motor down to ensure that it is meshing with the bevel gear correctly. Make sure you have that metal disc and screw in place.

01-17-2005, 12:28 PM
Aha! The problem has been located. I am missing the metal disc but I am guessing that can be replaced by anything similar, and the set screw had not been all the way screwed in. I am guessing all there is to do is to replace the screw and re-screw in the set screw?

Thanks for all the help Wolv, I really apreciate your taking time to help the less knowlageble.

01-17-2005, 02:07 PM
Yes, if you can find a piece of metal (or even a strong piece of plastic that won't deform when pressure is applied) that will fit in that space, you'll be good to go. Look for a piece of metal about 1.5mm thick. Once you have it in place, along with the motor plate secured, screw the set screw in until you encounter resistance. Then, screw it another couple turns. Test fire the gun and listen to the sound of the mechbox. If it sounds whiny/screechy, screw the set screw in another turn. Then, test fire the gun again. Do that until you don't hear any whiny noises. If at any time, the gun doesn't work, back the screw out, because that means the motor went in too far, and the pinion gear is jammed up tight into the bevel gear.

01-17-2005, 02:15 PM
Thanks alot. Problem solved! :)

01-18-2005, 01:18 AM
P.S. I've used thumbtacks as a motor spacer in a pinch. Just cut off the tack, leaving only the head. Then use a dremel and a vise/visegrips to hold it while you grind the tack part down. Then lay it on concrete & smash it nice & flat. You may have to grind the outer edges just a bit, as they're slightly larger than the stock spacer.

01-18-2005, 08:12 AM
Thats almost exactly what I did.

01-18-2005, 06:52 PM
Last question: Does getting a larger fuse (20 Amp) create any problems?

01-18-2005, 07:22 PM
Last question: Does getting a larger fuse (20 Amp) create any problems?
Just allows more current through to the motor. A larger fuse won't hurt anything by itself. However, if a gun is requiring a 20A fuse to work, there is excessive friction or resistance somewhere in the system, which indicates a problem. I'm no electrical expert, but I've run guns up to 450fps with 15A fuses, powered by 10.8v packs.

01-18-2005, 11:06 PM
O.K., because I was using 15 amp fuses, and now I have bumped up to a 20 amp becuase I got an eg-1000 (if you thought the Mp5 had a sweet rof before, now its like unbelieveable!!)

01-18-2005, 11:23 PM
Going to a EG1000 doesn't mandate, require, or benefit from using a higher-rated fuse as far as I know.