Ive got a makita 18v combi drill.... about 80% of the time when switched to high speed (in drill,drive or hammer action mod) the chuck spins but there is ZERO torque (you can literally stop it with your hand). Fiddle with the speed switch for a while and it works ok again...
Any idea what could be wrong and if I could fix it myself ? I thought perhaps it was something to do with brushes but i dont see brushes listed as a spare part for my particular model.
V-Low Voltage DC Motors may not have carbon brushes, all though some do. So I wouldn't worry about that.
It could be a clutch is not working properly, if the machine has one, because it's full of dirt and debris which is causing it to slip. It should be a simple clean and clear and get it working again.
It may be that the switching, because it has speed control, is not working correctly and not giving the motor full amps to keep the power on. From your description of playing with the control to get it going again. This may also be down to dirty or burning contacts. It may be possible to clean them, or they might be better replaced to prevent further damage to any sealed switching parts.
Depending on the age of the battery, it may also be in need of replacing. The motor works best on the amperage of the battery. Batteries get old and lazy and will hold voltage but not the full amps that they should. They can also be damaged by not recharging them properly. They also become weak through heating with heavy use, like drilling a brick wall under constant pressure, when they should be *pulsed*.
(*pulsed" Begin drilling under pressure. Release pressure to allow the motor to spin up to full speed for a second, then begin drilling again under pressure. Repeat this pulsing action until the hole is the depth you need. This helps prevent overheating of the battery and motor, so prolonging the life of the machine.)
If it were brushes can't see why changing speed would matter?
If fiddling with the speed change switch sorts it my first guess would be dirty contacts on that - or a dry joint on the connections to it. If the switch isn't expensive, replace it.
Is that "speed switch" an electrical one or just attached to a gear box? Whe you say "the chuck spins" do you mean you can rotate it freely by hand or does it run up to normal speed by power but takes no effort to stop. If you let the chuck go and retain power on does it run back up or stay stopped? Are there any noises other than motor whine?
Personally I'd be looking for a mechanical problem, clutch or gears not engaging properly.
I think Dave is right - its a mechanical issue... I took the drill apart - pretty scary... and it seems that the slider on top moves a small "nipple" on the top of the gear housing... The in turn moves a set of cogs in or out from low to high gear...
5 mins to take apart and about 45 mins to get back together. I dont think I "fixed" anything to be honest but it seems a bit better so perhaps i seated the slider on the switch a bit better.
'Switch' almost certainly suggests an electrical device. Lever, etc might be a better choice. Or even slider.
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