# Smart Car Pump



## SWF (Nov 23, 2007)

QMANDLL said:


> Hi. We are mucking around with a Smart Car water pump from EVWest. It is supposedly PWM, but they have no tech info on it. We have tried all manner of PWM at 5 and 12 V with no success.
> 
> Any comments?


Have you had any success getting the pump controlled with PWM? I have one as well and it runs fine at full speed with 12V applied to the positive and negative wires, but not sure exactly what signal the PWM wire is supposed to receive. I may buy myself a small PWM controller that has an adjustable frequency to see what works.


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## SWF (Nov 23, 2007)

I bought a small 12V PWM controller and confirmed you can just apply PWM output from such a controller directly to the 12V+/- input wires on the pump to control the speed and not use the wire EVwest has labelled "PWM" on the pump.

However, I have also learned by accident that reversing polarity on the 12V+/- pump wires will instantly cook the circuits inside the pump. I opened up the pump and there is some form of control circuit, likely a combination of PWM and one that shuts the pump down if there is no fluid in the pump.

Still not sure if I will use the remaining duplicate pump that I did not fry, or just get some Laing pumps that seem to be popular.


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## DrJeff (Apr 24, 2015)

I have 3 coolant pumps from a Tesla Model S. The pumps are made by Denko - but unable to read the part number.

The are 4 wire PWM controlled : +12v, Gnd, Tach, and PWM. I can get the pumps to run at full speed with +12v and Gnd applied, but I cannot get it to react to the PWM signal. Also tried 5v and 12v PWM signals.

I did get the pump speed to adjust by applying PWM directly to the +12v line, however the pump didn't slow gradually, it slowed somewhat (I did not measure flow) and then stopped completely below about 11.5v. I suspect this is not a good control scheme.

Anyone with ideas of how to gain PWM control of the pump?

Thanks
Jeff


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## DrJeff (Apr 24, 2015)

The Tesla coolant pumps are also sold as VariMax Intercooler Pumps.

They have four control lines...

+12v and GND
PWM and Signal.

PWM is a 5v, 2Hz signal (2 cycles per second)
(switching on for 0.25 secs, and off for 0.25 secs will set speed to 50%)

Signal is a PWM-like and indicates the pump speed.

Jeff


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