Makita Nail Gun GN900SE

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Hi - I have a Makita GN900SE gun. It is serviced regularly, by me, with oil, rings etc. Recently it started to run out of battery life quite quickly. So, I bought 2 new batteries. This didnt help as the new batteries ran out of power after 20-40 nails. So, I assumed it was the charger and replaced the charger. Still no improvement with batteries still dying after 20-40 nails.

The only thing left it can be is the gun itself. Can anyone point me in a direction as I have not got a clue what this could be?

many thanks in advance.
 
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Possibly battery contact/terminal issues inside the gun? Passlode guns can exhibit rapid battery discharge when the battery terminals are coated with black oxide.
 
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Thanks JobAndKnock for the response. I will strip it this week and have a look inside it.
 
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Thanks lostinthelight It seems this is out of stock atm but I get the idea.
 
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Since I posted this I have tried the terminals and cleaned them. The batteries are charged to 8 volts, tested using multi-meter. The light on the gun will switch from flashing green to alternating green/red flashing and then to constant orange. It does this with all 4 new batteries. It will fire only 2-4 nails before this happens. Once this happens the multi-meter shows that the battery charge has dropped to 7.93 volts.

I stripped the gun and inserted a battery and pressed the trigger. The ignition system gave a spark at each press.

The only electrical components in the gun are the switch and the spark unit. I don't suspect the switch but could the spark unit be the problem?
 
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Yes. I've had igniters fail in the past a couple of times, although when that happens the gun normally won't spark. Have you checked if the safety lock-out is working correctly?
 
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Thanks JobAndKnock If I am thinking of the same bar as you (the bar that is depressed with the contact top etc to allow the trigger to be fully depressed) then this is working fine. After a few nails the gun, when the light goes constant orange, the gun does everything as if it is going to fire but there is no power to the unit. The igniter doesnt produce a spark and the fan does not start up.

There is, imho, an electrical problem. There are, of course, 3 main electrical components. The igniter, the switch and the motor.
 
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Ive just tried it again and when the gun has fired a nail the motor/fan runs as normal for a couple of seconds and then runs roughly, as if its running out of power
 
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In order to generate the sorts of voltage required to make the spark there must be some form of capacitor on the igniter board. Know any radio or TV repair folk who would be willing to check the igniter out?
 
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I've just been given a help desk number for Makita so I will give that a go this morning.
 
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sounds like a faulty discharge protection circuit. If you can find it, it can be bypassed with a bit of wire.
 
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