Hot Electronics
It's normal for the electronic speed control (ESC) or mechanical speed control (MSC) and resistor (and the battery and motor) to get hot after the model has completely drained a battery pack. With that in mind, it's a good idea to let the electronics cool down before installing another battery pack and continuing to run your model. Running battery packs back to back can overtax the electronics, which will lead to premature failure. Always pay attention to the temperature of your battery, speed control annd motor.
Battery is hot but the ESC and motor are cool.
The battery is too small for the vehicle size weight or running conditions. Use a battery with a higher capacity or install a smaller pinion gear. If only one cell is getting hot and the others are not, the battery must be replaced. Never run a damaged or failed battery pack.
Battery, ESC and motor are all hot.
The system is under high load. This can be caused by operating style (abusive driving), a high resistance environment (water, mud tall grass etc...) or binding somewhere on the truck. Install a smaller pinion gear or remove the cause of the high load. Test the drive line by removing the motor, holding the truck in the air and spinning the spur gear by hand. The rear wheels should turn with no resistance at all (all 4 wheels should turn in 4 wheel drive vehicles). Spin the front wheels to make sure they also spin with no resistance. Test the motor by turning the pinion gear. If the motor is binding, give it a thorough cleaning with motor spray and then re-lube the bushings with light machine oil and try again. If a thorough cleaning doesn't fix the binding problem, rebuild (Brushless) or replace (brushed) the motor. If you find resistance you must locate the source and eliminate it.
Battery is cool but the ESC and motor are hot.
The electronics are under high load. This can be caused by operating style (abusive driving), a high resistance environment (water, mud tall grass etc...) or binding somewhere on the truck. Install a smaller pinion gear or remove the cause of the high load. Test the drive line by removing the motor, holding the truck in the air and spinning the spur gear by hand. The rear wheels should turn with no resistance at all (all 4 wheels should turn in 4 wheel drive vehicles). Spin the front wheels to make sure they also spin with no resistance. Test the motor by turning the pinion gear. If the motor is binding, give it a thorough cleaning with motor spray and then re-lube the bushings with light machine oil and try again. If a thorough cleaning doesn't fix the binding problem, rebuild (Brushless) or replace (brushed) the motor. If you find resistance you must locate the source and eliminate it.
Either the motor is too hot or the ESC is too hot but the other component is not.
Reduce gearing and/or voltage so that the higher temp item is allowed to run at a more appropriate temperature. Check for adequate airflow to the higher temperature item (ie: make sure the ESC fins are not obstructed). Test the motor by turning the pinion gear. If the motor is binding, give it a thorough cleaning with motor spray and then re-lube the bushings with light machine oil and try again. If a thorough cleaning doesn't fix the binding problem, rebuild (Brushless) or replace (brushed) the motor.