Did you mean unplug the SERVO and see if the resistor overloads? the resistor is on the amplifier board. I tried that and it does not overload if the 1-5 pin electrical plug on the servo is unplugged.
the rebuilder is telling me that if the motor in the servo works it should not be overloading??? I am skeptical at this point so glad to hear that it can still short. I will pull a working servo from another car and plug it in and see if that doesn't fix the problem. first I have to come up with some replacement resistors to solder onto my blown up amplifiers....
Yes, I meant unplug the servo, not the amplifier. Sorry about that.
If the amplifier quits shorting when you unplug the servo 1-5 plug, then it's either the servo or the Auxiliary electric water pump. I believe you said you already checked the water pump, so that leaves the servo. Try another servo and see what happens. Just swap plugs to the test unit without mounting it.
Regarding your amplifier, do make sure that none of the transistors have fried, as well. If I remember correctly, the transistors are of the BR series, and are very common, cheap, and easy to find. If in doubt replace them anyway.