I have an old coffee maker that is activated by a switch which feeds a relay. I think that the relay failed.

The relay coil voltage is is 24v. I think the part number is SRUDH S 124DM1. The circuit appears to have a 120 to 24v transformer and a half bridge and capacitor to rectify the current to 24vDC

What would happen if I replaced this coil with a 12v one? enter image description here

  • 4
    \$\begingroup\$ If you're lucky, just a little smoke. \$\endgroup\$ Nov 23, 2015 at 12:24
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    \$\begingroup\$ I would be more concerned about the black stuff on the board between the two capacitors towards the bottom in the picture. It could be glue (which would be OK) or it could be leakage from the capacitors (bad.) \$\endgroup\$
    – JRE
    Nov 23, 2015 at 13:02
  • \$\begingroup\$ I think it is glue. This whole board is coated in some sort of plastic or resin. \$\endgroup\$
    – gbronner
    Nov 23, 2015 at 13:50
  • \$\begingroup\$ Wow. Tough crowd! I tested the relay by prying off the top and using 2 9v batteries to test the contacts, and it appears to work. So I'm going to replace the capacitors next. \$\endgroup\$
    – gbronner
    Nov 24, 2015 at 13:58

2 Answers 2


You could add a resistor and make a '24V' relay, however it will draw about twice the current as the original relay. This is not a good idea- the rest of the circuit may not function properly and cause other problems. These parts are not particularly expensive- suggest you get the right part. Pay attention to the current rating too.

By the way, the designer of that PCB was most likely operating in an extremely cost-constrained environment. That they chose to use a 24V relay rather than a 12V relay tells me that they were likely using a dropping capacitor supply and had to use a lower current relay to keep the size and cost down- so your 12V relay + resistor is likely out. In massive quantities the 24V relay will be slightly more expensive than the 12V relay because the coil requires more turns of finer wire. Usually 12V and below are the minimum cost parts.

  • \$\begingroup\$ If you use a larger than normal resistor to keep your current the same and place a large electro across the resistor it will work .The question is is it worth it? \$\endgroup\$
    – Autistic
    Nov 23, 2015 at 19:57

Yes but you will have put a resistor in series with the coil to limit the current. That will require you to do a slight mod to the board. What value resistor I hear you ask??? Well that may need some detective work because you need to know what current the lower voltage coil will draw at its rated voltage, work out its equivalent resistance and then add that resistance because you are applying double the voltage. Simple ohms law stuff.


Get a 24v relay from your local electronics shop, and that will save a ton of grief.


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