I am not very experienced in electronics. I have a water softener installed at home, and recently it stopped working.

I was looking for things that could have failed, and found this board with what seems like a leaked capacitor:

Board from the top

Board from the bottom

board from the front

However, this blue capacitor does not have any markings on it, and I can't find any reference online about it to order a replacement.

Any ideas on what it could be?

  • 7
    \$\begingroup\$ looks more like a ferrite coil than a capacitor. \$\endgroup\$
    – glen_geek
    Aug 23, 2021 at 18:26
  • 4
    \$\begingroup\$ It is a coil/inductor. \$\endgroup\$
    – jay
    Aug 23, 2021 at 18:29
  • 6
    \$\begingroup\$ Inductor, possibly custom wound for that circuit. The "leakage" around it looks like adhesive to stop shock/vibration. You probably have to look elsewhere for the failure. \$\endgroup\$
    – user16324
    Aug 23, 2021 at 18:45
  • \$\begingroup\$ As others have said it's a ferrite drum (unshielded) inductor and no doubt just fine. Check that that relay is working and not just worn out (eg. clicks but doesn't function). \$\endgroup\$ Aug 23, 2021 at 19:41

2 Answers 2


It is not a capacitor, it's an inductor, and it's not leaking, it is held firmly in place with glue.

  • 1
    \$\begingroup\$ In fact, inductors usually do not have any fluid in them, so they cannot leak. \$\endgroup\$ Aug 24, 2021 at 8:56
  • \$\begingroup\$ @user253751 what if the wires' insulators melt? \$\endgroup\$ Aug 24, 2021 at 12:35
  • \$\begingroup\$ @RohatKılıç then I would guess it probably catches fire. \$\endgroup\$ Aug 24, 2021 at 12:54

Power coils radiate heat better when not mating with insulation on FR4 board especially with lower design margins to thermal runaway. PU adhesive with high tensile strength would be used.

Resistors tend to be derated 50% when nearby but will also be elevated if lower temps are needed.

Caps are already thermal insulators with thin foil and dielectric and are usually also bonded to board or nearby parts with a more damped flexible Polyurethane. E-caps must have a popcorn lid so this part has none which is an obvious takeaway.


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