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Electric Water Pump Control

Darryn Green

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I have a Davies Craig electric water pump that I would like to control with the link, the davies craig controller (that I could buy for more $$$ but I would rather not) works with a combination of variable voltage and duty cycle from the research I have done, here is what I found, Phase A: The EWP pulses at 6V-- 10 sec.ON, 30 sec.OFF until coolant temperature is approx. 20 degC below the 'Set' temperature. Phase B: The EWP pulses at 6V -- 10 sec.ON, 10 sec.OFF until coolant temperature is approx. 5 degC below the 'Set' temperature. Phase C: The EWP is ON and supply voltage increases linearly with temperature from approx 5 degC below to 'Set' temperature. At 'Set' temperature the EWP is at full output. So is it possible to set up an output to do the above? I had a quick look and could see how to set up a PWM output but thats about as far as I got, would be good if it could be setup in a sort of open loop mode based on the ECT as the engine will not be running a thermostat, also could it be set to run for a set time after the engine is shut down? Any info or if you could point me in the right direction would be great! thanks alot Darryn

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Hi Darryn

You can drive the pump direct with the aid of a solid state relay.
This is due to the current required to run the pump being greater than what the ECU can deliver.

With the solid state relay you can then PWM control  the pump based on engine temp. Running low duty cycles at cold temps and increasing as the temp increases.

Unfortunately there isn't the ability to keep it running after shut down inless you have an override switch which could run the pump full speed.

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Hi Darryn

Lucky it is nearly possible, would be nice if Link made it easier.

To act like the Davies controller, you need the following.

To give on/off @ min 5V PWM at low temps you have to use Timer 1, Activation = Virtual Aux 1, Max Time = 40 sec, Polarity = Reset When On. Then set Virtual aux output 1, Switch Logic = Cond 1 AND 2 AND 3, SW Cond 1 = Timer 1 > 39.99, SW Cond 2 = RPM > 600, SW Cond 3 = ECT < (Your Set Temp - 20).

Use Timer 2, Activation = Virtual Aux 2, Max Time = 20 sec, Polarity = Reset When On. Then set Virtual aux output 2, Switch Logic = Cond 1 AND 2, SW Cond 1 = Timer 2 > 19.99, SW Cond 2 = ECT > (Your Set Temp - 20)

For running after stopping the engine, I have a race car and the power to the LINK is always on. So you need to retain power on to the LINK ECU.  With the above control and engine stopped the pump will keep running until the ECT drops below your Set temp - 20. The Link cannot do a shut off timer sorry, one option of fitting a external turbo cool down timer relay which controls the power to the LINK.


Setup the working aux output as GP PWM, Frequency = 80 Hz, SWOffTimer = 0, Switch Logic = Cond 1 OR 2 OR 3, Sw Cond 1 = Timer 1 < 10, Sw Cond 2 = Timer 2 < 10, Sw Cond 3 = ECT > Set Temp.

SET the Aux PWM graph, as single axis X as ECT (axis y = none). Now the hard part, what values should you enter?? It will be trial & error method, but start with your ECT at (set temp - 5) & below = 20? (being 5 Volts at the pump) and ECT at (set temp + 5) & above = 100 (full voltage). The idea is the LINK will interpolate between and settle hopefully around the set temp.

I heard you cry HELP, it should not be this hard. Just remember I any on your side. So Simon of Link what are your comments???

Cheers and good luck


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