C12 Speed Varies

[Mini Me]

My beloved C12 seems to have a issue with maintaining a constant speed in either gear and with either battery. This drill has done many years of sterling work and been dropped off ladders, kicked across floors and generally had a hard life. The problem recently reared its ugly head when it started surging and the speed goes up and down though it still gets the job done. Any ideas on what it is? I suspect the speed controller but someone may have had the same issue and knows for sure. Thanks.

Chris

 

[TylerC]

How old is your drill? This sounds similar to an issue that we had with the C12 a long time ago.

 

[Rick Christopherson]

Chances are the problem is the variable speed trigger, and not the main controller. Inside the trigger is a solidstate variable resistor with a soft-tip wiper. None of the drill's power passes through the trigger. It is only a low-power signal that controls an oscillator in the controller.

If you try to take the drill apart yourself, just be aware that there are tiny flat-spring clips on a couple of the green pieces that give them their detent positions/movements. You have to pay attention to where they go.

 

[Mini Me]

I think I will pass on pulling it apart myself, is it a simple matter of cleaning the wiper? I bought it when they were new onto the market in Australia so it is fairly old.

 

[Rick Christopherson]

Yes, exercising the wiper has been known to alleviate the problem. My C12 is one of the originals, and when it acts up, I simply exercise the trigger with a couple of full-pulls. It cleans the wiper and film resistor.