dkh wrote:
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.)