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High Water Temperature Diagnostics

On most generators Welland Power fit two different water temperature detection devices, a switch and a sender.

The Switch, supplied by the engine manufacturer is used to shut down the engine in the event of the coolant becoming too hot. On fault, it closes to earth.

The sender is used to give a reading of engine temperature on the panel. We do not suggest this is used for protection. The resistance changes depending on the coolant temperature. It is normal not to get a reading below about 60 degrees (the same as your car).


!Remember if you take off the radiator cap it may be pressurized and very hot! Take appropriate precautions!


The first item to check is has the engine genuinely overheated? If it has - the coolant will be very hot in the block (it may not be hot in the radiator) and the engine coolant switch will be closed to earth. In the event of genuine overheating, you should check the coolant level, the coolant is the correct type (we suggest Perkins ELC), the radiator is not blocked and the thermostat is working correctly and not corroded or jammed closed.


Remember! If you have recently filled the radiator, it is possible that air has locked in the system and the one or more of the sensors are not in coolant!


If the engine does not appear to have overheated then this could be down to electrical issues.

Initially check the coolant setting for shutdown in the controller. This setting corresponds to the reading on the sender, however as per above, we do not suggest using the sender for shutdown. You should therefore raise the temperature limit as high as possible. In the event of the engine over heating the engine switch will perform this function.

Firstly we suggest disconnecting the engine temperate sender - Important: leave the switch connected! The engine will be protected by the switch, but no coolant temperature reading will be available.
Now run the engine and see if the fault persists. if the switch shuts the engine down, the switch may be faulty, assuming that the coolant is over the switches limit. If the fault does not persist then there is either an issue with the sender, or the senders earth.


Secondly we suggest checking the switch. When the engine is cold it should be open to earth. If it isn't then it needs replacing. Remove and replace the switch.

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