Troubleshooting 12v pwm water pump motor

Thread Starter


Joined Sep 11, 2020
Hello all, I hope this is te right place to post it otherwise feel free to move it to an appropriate subforum.

I have a problem with my pc water pump and now I'm trying to find out if there is a way to fix it. I don't know where to start troubleshooting or what kind of values I should be looking for with my multimeter.

In the attached image you will see the circuit of the water pump and there are 6 coils below it with marked 3 connector points and a common ground I believe (where all 3 coil wires come together).

I know I was the problem, I applied around 19v and 2a to the motor when it died (I thought it can take 24v). When I unsoldered the points (1, 2, 3) to look at the windings I didn't see anything burnt and nothing smelled bad either which is where my electronics troubleshooting knowledge ends.

I did test the resistance between the 3 points (P1-P2, P2-P3, P1-P3) and all show around 12.5 ohms. The resistance between the common ground and points (CG-P1, CG-P2, CG-P3) is around 6.2 ohm (half or close to half of the value measured between points 1, 2, 3).

Now my question is, does the winding resistance indicate that the coils are fine or should I try to rewind them with new wire?

If it's an issue with one or more components on the pcb how should I go about trouble shooting it?

The pcb is marked with 0138-04 and e258078 but my searces weren't successful. The components are bigest IC (A 494967 1710 502U), bigger transistor or diode of some sort (1625 LG), smaller transistor or diode (SS14 - found some info on this one) then there's support power supply? (1AM3) then there's some small resistors (000, 010, 202, 302) and bunch of other small unlabeled components.

When I connect the power supply to the circuit now at 10v input I get a reading of about 0.8v-1.0v I also don't mind soldering a replacement circuit with different components if it will allow me to still use this 12v rpm pc water pump.

Any information you can provide is much appreciated.



Joined Jul 18, 2013
A shorted turn is virtually impossible to tell with a resistance check, also it is most likely to be electronic fault, this is a ECM, electronically commutated motor.
Obtaining a schematic is usually next to impossible, which leaves checking all the solid state components you can, and/or reverse ingineering as much as possible..

Thread Starter


Joined Sep 11, 2020
Thank you for your answer MaxHeadRoom. So I guess it's not worth troubleshooting this circuit. Maybe finding an existing circuit from another device would be a better way, unless that too would not work because the coils winding number may not be correct to what that "new" circuit was designed for?