I've used rubbing alcohol for some time, and have had no problems with it. So if it works for you, I say use it. If you REALLY are afraid that alcohol is bad for your contacts (its bad for your liver anyways), then you can try a pencil eraser. First you have to take the circuit board out of the cart (duh), so it involves some unscrewing. But if you rub the pencil eraser over the contacts, they will come clean with no chemicals. I use this method if the contacts just WON'T come clean no matter how much rubbing alcohol I use.