I'd say to pick up a cheap digital voltmeter (Harbor Freight has one that's usually on sale for under $5, and they had a coupon for it for FREE out a while back in the Sunday coupons) and use it to check the tops of the drivers, or anywhere else you can easily probe, to see if it's getting power. I know these can be a bear to take apart, so I'd examime where the power goes from the wheels into the locomotive carefully. Make sure it's not related to the drivng rod position or something. (I sold mine quite a while ago, so I'm not 100% on how the power goes up into the motor).