Simpson Minimax 10 Trips circuit breaker on hot or warm?

We purchased a second hand Simpson minimax 10,which trips the circuit breaker / safety switch on Hot or warm ok on cold. so far done the following
1. Tested the heater element and ok
2. checked for low resistance to earth on heater element and ok
3. replaced the heater element
4. checked for low resistance to earth on timer switch and hot / cold /warm switch and seems ok.
5. Tried next door neighbour safety switch and same result.
Noticed that motor is running very hot on cold cycle. ?
6. Checked thermostat and looks ok.

Mark
May 2017