We have an instant gas hot water system that is not initiating.

I've traced it to the water flow sensor not signalling when water is flowing. After inspecting the housing, the magnet is spinning freely and easily, free of debris.

I checked the sensor readings and it seems faulty. It's a 3 wire sensor, likely a hall effect sensor of some sort. Voltage across black and red is 5.01V and across black and white is also 5.01V (so I'm guessing its normally closed / NPN).

If I understand it correctly, I should see a change in voltage on the load wire (black + white) when the magnet spins across the sensor, but I'm not seeing any movement of voltage in either black+white or black+red.

Unfortunately the supplier has no more replacement flow sensors and the model it's used in is discontinued.

Naturally, I pulled apart the flow sensor (see photo below), cleaned off the potting agent and see it's a 3-pin IC marked with "W10" and "1095" below.

BUT, my Googling for hall effect and those numbers doesn't pop anything. I was hoping I could replace it and get back to having nice warm showers again :-]

Does anyone know of an equivalent IC or how I can identify / order that IC?

Much appreciated.

Flow Sensor PCB with IC W10 1095

  • 2
    \$\begingroup\$ Incidentally, "1095" is probably week-year. So, March 1995. \$\endgroup\$
    – rdtsc
    Jul 29, 2020 at 13:03
  • \$\begingroup\$ Ooh... OK. Is that quite a common thing for IC markings? \$\endgroup\$
    – Jaans
    Jul 29, 2020 at 14:22
  • \$\begingroup\$ It is fairly common. But sometimes it is encoded instead; depends on the manufacturer. Usually the "part number" and "date code" are present on every IC though. \$\endgroup\$
    – rdtsc
    Jul 29, 2020 at 14:29

1 Answer 1


I've found these guys being sold:

Hall switch EW510 Asahi into Hall component W10 treadmill speed control brand with Hall ew510.

enter image description here
Source: Chinese seller page

They have the W10 marking. If EW510 is really your W10 component, then here is it's datasheet.

It doesn't seem like a very easy component to buy, so maybe you could use the datasheet to guide you into buying another hall effect sensor IC with compatible characteristics.


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