MAW Solutions Ltd    Henfield, W Sussex    Phone: 01273 493343    Email: info@mawsolutions.com

The manufacturers of our electric water pumps, Davies Craig, have developed pump speed controllers which are designed to ensure that the volume of coolant being pumped around an engine and through the radiator is varied according to how hard the engine is working. The Controller uses a probe located inside the engine’s water jacket (eg inside the thermostat housing) to sense engine temperature, and translate this temperature into a variable voltage. Then,  the higher the temperature, the greater the output voltage, and so the faster the pump rotates, and the greater the volume of coolant flow. . 

A pump controller is only required in installations where the electric pump is the only pump. If the electric pump is installed to assist a mechanical pump, then it should be controlled by a switch. Basically, the Controller is performing two main functions. Firstly, it is acting as a thermostat by limiting coolant flow until the engine has warmed up - initially pulsing the coolant, and then gradually speeding the pump up. And secondly, once the engine has warmed up it varies coolant flow to maintain engine temperature at the preset level, so minimising wasted pump power and optimising engine operating conditions.

The Controller has push buttons which allow you to select the target engine temperature (the set point) at 75,  80,   85, 90 or 95 deg C.  It also has various led’s which indicate temperature, pump running etc, and also offer a user-friendly range of facilities, including a built-in diagnostic system, using the 9 integral LEDs to display fault conditions.  And there’s a separate red warning led which can be mounted in an appropriate position on the dashboard, in the driver’s eye line. 

From July 2009 a new model, the Dual Controller has been launched. Like the previous model, which hit the market in late 2006 and has proved very reliable and popular, this microprocessor-based unit will control the speed of all three pumps in the Davies Craig range - and in addition it will now switch the electric fan on and off as well.

Key Features of Dual Controller  (part no. 8020):

Input Voltage            12 volts - 13.5 volts Output Voltage 6 volts to 13.5 volts Maximum Output Current 12 amps Controlled Engine Temp 75 / 80 / 85 / 90 / 95 deg C Fan Cut-In Temp 3 degC above set temp Sensor Type Thermistor Heat Soak Run-On 2 minutes after ignition off Indicator LEDs Temp, Power ON, Pump mode and Test Size 101mm x 95mm x 35mm Weight 90 grams (3.2 oz)

The Controller needs to be mounted inside the car, away from the harsh under-bonnet environment, and is supplied with a sensor in a waterproof housing, and a  colour-coded wiring harness for connection to the pump and fan. The sensor has a  1/4” BSTP thread which can either be screwed directly into a suitably tapped hole in (eg) the thermostat housing, or mounted into the top hose adaptor which is supplied in the box.   

In operation, the Controller begins to pulse the EWP (10 seconds on, 30 seconds off) as soon as the engine is running, to avoid any risk of local hotspots developing. When the engine warms to 20 degC below the Set Point, the pulsing changes to 10seconds on, 10 seconds off; and then as the Set temperature approaches, the EWP goes into continuous run mode, with the speed of its running determined by the Controller so that Set Point temperature is reached and then maintained.

To reduce heat-soak effects after engine shutdown, the Controller automatically keeps the pump (and fan) running at full speed for 2 minutes, or until the sensed temperature is reduced to Set Point - 5 degC, For more information on the Digital Controller, or on how to install it, click on the link below.

Please feel free to phone us on 01273 493343 to talk about your application.