Having got a 300TDi Disco, one is always concerned about overheating issues as the 300TDi is notorious for cooking the head if the water level drops slightly. This is due to the thermostat housing being the highest point in the engine and the water pump being very high. It doesnt take much coolant loss for te pump to suffer from cavitation and the engine to overheat. 
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Many moons ago (about 10 years ago) some fella produced a magic box to give warning of low water level and, hopefully, enable the owner to stop before it was too late. Unfortunately this system appears to have disappeared from the annals of Landrover websites. So I thought I would have a go!!!!
Being blessed with aircon on this beast, I have a couple of electric fans mounted in the front of the radiator, so these were the obvious choice to use.
The criteria that the system had to comply with is as follows :-
To be fail-safe - ie if the sensor or sensor wiring failed, then the warning would still work.
To show that the system was functioning correctly on power up.
To automatically show low water level
To allow manual switch-on of the fans when required.
To automatically switch the fans on when the coolant reaches a pre-determined temperature.
To still work as "normal" air conditioning fans when fault conditions are not present.
To this end I had to buy the following extra components (as well as the controller box)
manual fan switch (with warning light) (I had an old Kenlowe switch)
Range Rover low water sensor cap (PRC7925)
Thormostat housing elbow (ERR3738)
Overheat sensor (PRC3359)
P5 pin relay
various wires, connectors and sleeving
Here are a few pics and videos of the final system.
Low Water Sensor and magic box
Additional Fan Control Relay
Overheat sensor in Thermostat elbow
Power and Ground taken from Fuel pump
Power up sequence - Low coolant warning light
Power up sequence on fan control light and manual override
Power on sequence and overheat overide (simulated)
"Magic box" is available in 3 options :-
1) low water level warning only.
2) low water level and fan control.
3) low water level warning, fan control and overheat control.
From £25. NB. Does not include external items such as low water sensor, fan control relay or overheat switch.
.Many moons ago (about 10 years ago) some fella produced a magic box to give warning of low water level and, hopefully, enable the owner to stop before it was too late. Unfortunately this system appears to have disappeared from the annals of Landrover websites. So I thought I would have a go!!!!
Being blessed with aircon on this beast, I have a couple of electric fans mounted in the front of the radiator, so these were the obvious choice to use.
The criteria that the system had to comply with is as follows :-
To be fail-safe - ie if the sensor or sensor wiring failed, then the warning would still work.
To show that the system was functioning correctly on power up.
To automatically show low water level
To allow manual switch-on of the fans when required.
To automatically switch the fans on when the coolant reaches a pre-determined temperature.
To still work as "normal" air conditioning fans when fault conditions are not present.
To this end I had to buy the following extra components (as well as the controller box)
manual fan switch (with warning light) (I had an old Kenlowe switch)
Range Rover low water sensor cap (PRC7925)
Thormostat housing elbow (ERR3738)
Overheat sensor (PRC3359)
P5 pin relay
various wires, connectors and sleeving
Here are a few pics and videos of the final system.
Low Water Sensor and magic box
Additional Fan Control Relay
Overheat sensor in Thermostat elbow
Power and Ground taken from Fuel pump
Power up sequence - Low coolant warning light
Power up sequence on fan control light and manual override
Power on sequence and overheat overide (simulated)
"Magic box" is available in 3 options :-
1) low water level warning only.
2) low water level and fan control.
3) low water level warning, fan control and overheat control.
From £25. NB. Does not include external items such as low water sensor, fan control relay or overheat switch.
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