HELP New Bits dont work at all

[avengerhed]

hey all i just bought 2 bits, both 27 mHz (for different ppl) and neither of them work....i have had 3 other brand micro cars and they are all find .... these will charge, and if i physically jump connections the motor/steering will work, but its as if there is no Controller-to-car connection.....any help would be greatly appreciated....i have soldering equip and a fairly good EE knowledge.... please help if you can, thanks so much
-dave