On most generators by Welland Power and other manufacturers you will find two different water/coolant temperature detection devices fitted, a switch and a sender.
The Switch, often 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, but can also be used by a controller to shut down at a specified temperature. The resistance or voltage (depending on the sender fitted) changes depending on the coolant temperature. It is normal not to get a reading below about 60 degrees (the same as your car).
So why might the generator be shutting down?
The generators coolant is too hot
Coolant heats up as the engine is running; the coolant is pumped (by the 'water pump') through the radiator where the engine fan blows ambient air through the radiators matrix to reduce the coolants temperature.
Check the temperature of the coolant.
!Remember if you take off the radiator cap it may be pressurized and very hot! Take appropriate precautions! The coolant may also be very hot if it has overheated and steam may escape when opening the cap.
If the coolant is too hot the coolant switch may have shown a fault (normally by closing to earth)or coolant sender has indicated a reading (either resistance or voltage) that is too high - in both these instances the controller will take action to shut down the set. The coolant could be too hot because:
- The load on the engine is too high, meaning the coolant cannot be cooled fast enough; this leads to the coolant getting hotter and hotter until the coolant switch closes on fault causing shutdown. (or the controller shutting it down by reading the sender). - In this case reduce the load on the generator.
- The radiator matrix has gathered dust / oil and the air cannot pass in sufficient quantity, leading to the same effect as per 1. above. In this case get a professional to clear your radiator.
- The inside of the radiator has corroded and the pipes that carry the coolant have clogged. This can happen due to using the incorrect coolant / water mixture, or incorrect type of coolant, or failing to change your coolant at the specified intervals. This leads to the same effect as 1. above also. In this case you will need the radiator power flushing - but you might need a new radiator.
- The 'water pump' may have failed, leading to the coolant not flowing around the system. In this case you would require a new water pump. Note: In this instance the coolant in the radiator may still be cool, as it is unable to be pumped from the engine to the radiator.
- The thermostat has failed; the thermostat opens as the engine gets warm to allow the air to flow around the radiator. If the thermostat has failed, you will need to fit a new thermostat. Note: In this instance the coolant in the radiator may still be cold, as it is unable to flow from the engine to the radiator.
- If you have recently filled the unit, there could be an airlock in the system, meaning the amount of coolant in the system is too low and getting too hot. In this case add more coolant, after releasing the air lock.
- It could be the unit is shutting down too early if it is set to shut down on the sender. Because the sender sends a resistive or voltage value to the controller, the controller then converts this into a temperature. Check the controller set point is correctly for the engine.
If the coolant is not too hot, it could be because:
- The thermostat has failed; the thermostat opens as the engine gets warm to allow the air to flow around the radiator. If the thermostat has failed, you will need to fit a new thermostat.
- The 'water pump' may have failed, leading to the coolant not flowing around the system. In this case you would require a new water pump.
- The coolant switch has shown a fault incorrectly to the controller (normally by closing to earth).
- Check for a closed circuit to see if the switch is opening / closing correctly and for broken wires (a coolant switch wire that has shorted to earth will also cause this fault.
- Something conductive touching the switch and the engines frame at the same time would also display the same symptom.
- The coolant around the switch is too hot (whereas it is cool in the radiator) this indicates either a water pump or thermostat failure.
- The coolant sender is displaying a value that is too high. There are a few possibilities for this:
- The sensor is not in the coolant and is therefore reading the temperature of the air (underfilled / air lock). Take it out, make sure it is in coolant and reseat it. The coolant may also be very hot if it has overheated and steam may escape when removing the sender.
- The coolant around the sensor is too hot (whereas it is cool in the radiator) this indicates either a water pump or thermostat failure.
- The electrical resistance or voltage of the circuit it not correct - the sensor may have failed or there may be a fault in the circuit. Measure and test it independently of the controller and confirm it is working to its specification.
Specifically for Welland Power generators fitted with a switch and sender
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, or one of the items above. You can safely run the engine without the sender connected.
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.