I have a Pierburg CWA200 electric water pump that can be controlled by a PWM signal from my ECU, I will shortly start the engine bay wiring using parts of a Rocketeer loom. I am trying to figure out how to wake the pump up, according to what I have read it needs a full 12 volt pulse to the PWM pin for just three milliseconds. Would it be possible to take a 12v feed from the ignition key when in the start position? I would take the feed from the signal wire before the relay to prevent any current spikes, will this work? will a 12v pulse back feed and damage the ECU? I have read putting a diode in the PWM signal wire will badly affect the signal. My problem is that the ECU manufacturer isn't helpful due to me buying an ex Rocketeer ECU rather than a new one.
No way you are going to be able to manually time a 3ms pulse so aside from building a dedicated one shot circuit (multivibrator?) I think I'd try just hooking it up normally and see if it runs.
Jim
I don't think it matters if you waken it up with a five second or even a one minute burst, you can run it flat out just by connecting 12v all the time. It's more about whether a 12v back feed into the ECU will damage it. Sadly the ECU manufacturer is being bloody minded and not helping with any information. They say in some of their literature that the ECU can control EWO's with a PWM signal, it's just waking the pump up. I have trawled the forums but no definitive answer other than a diode messes up the PWM signal.
Is your concern that it needs a 12v pulse every time it starts, or just after it has sat for awhile? Must be the former otherwise you'd just hook it up to a battery I guess.
It used to be that any electronic component would handle 50v as long as it wasn't conducting. So in cars backfeed was never an issue. I'm not sure if that still applies with 5v references for sensors but to drive a motor it has to. Any 12v motor is going to produce voltage spikes, sometimes well over that level and a square wave drive is particularly bad about that. In addition you have inductive spikes. Remember how a coil works, it produces a spark on field collapse. All motors have that going on hundreds of times a second so any circuit that drives them has to handle it. Even with a direct DC motor I don't think it can be avoided and PWM motors are usually three phase so they are constantly generating voltage spikes. Very noisy electrically.
But I'm not sure if that helps much if you need a 12v pulse to start. Kind of like a peak and hold injector in a way I suppose, but wait. PWM drives as a rule deliver full voltage when conducting, they just control the speed by reducing the pulse width. So you should already have your full 12v pulse, and 3ms is a pretty short one. Giving the motor a full speed command should easily exceed that I'm sure. Maybe that's why they won't answer you. Hate to say it but those kind of guys can be pretty arrogant, they might think that if you are messing with this at all you should already know that.
Anyway, HTH but trust and verify of course.
Jim
This CWA controller was recommended to me by a respectable fellow. I've purchased it, but not yet gotten to the point of installing or using it.
https://tecomotive.com/store/en/tinycwa/tecomotive-tinycwa
Yes, you would definitely need a driver (controller?) to use the signal from the ECU and power the pump motor. Sounds like that's what you have there.
From my experience with the RC airplane motor on my HVAC blower fan, not a bad idea to get a driver that is rated significantly higher than the motor draw and then use a breaker rated even higher. I found that itty bitty motor was capable of blowing 40 amp fuses after about 1/2 hour at full speed. I now have a 60 amp resettable breaker powering it. The alternator needs to keep up as well. It does move a lot of air though. I would not be surprised to see similar results with an EWP. Most of the time you wouldn't need that level of power, maybe never. But if you did...
Jim
Quote from: Roverbeam on May 28, 2026, 08:43:27 AMThis CWA controller was recommended to me by a respectable fellow. I've purchased it, but not yet gotten to the point of installing or using it.
https://tecomotive.com/store/en/tinycwa/tecomotive-tinycwa
I did know about that controller, it's prime advantage is that you can program it to leave the cooling fan and EWP running for a minute or two after the engine is switched off. I am just trying to eliminate too many controllers etc occupying the limited space but if I have to use it I will.
Jim, the nice thing about the Pierburg pump is that the PWM controller is built into the pump, all you need is a 20 amp supply, earth and a PWM signal. I am going to control the heater fan with a PWM controller, I have no idea what model Buick it came from but it's early nineties and thought a 40 amp controller would work but maybe not.
https://www.instructables.com/Use-an-Arduino-to-Drive-a-Pierburg-CWA200-Car-Elec/