Help Testing Relay

Hello, 

You will need a Ohms meter to measure the contacts and a 12v power supply to power the coil 

in a spa or similar they have a relay for heater or pump and also 1 in series for protection purpose,

if the relay has wires to it then you only need to disconnect 1 of the wires to the coil and put the power supply onto relay.

If  these relays are soldered to a board it makes it awakward as there will be a diode across the coil, so the power supply can only be connected 1 way around 

https://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=1308242_T92&DocType=DS&DocLang=English

You can see from the datasheet these operate from 12 Vdc across the coil.

You can measure the impedance of the coil using the pinout in the datasheet. If it is around 86 ohms, the coil should be okay.

You can measure the contact impedance, unpowered, the datasheet indicates which contacts are open and which are closed. (Measuring about infinite and zero ohms)

If you apply 12V across the coil, the relay should click and the contacts should change state (measuring zero and infinite)

If the card is disconnected from the system you can probably do these tests without removing the relays from the card, It may be worth checking what is connected to the relay on the card to know for sure if they can be tested in-circuit.

As acdc90  indicated you need to be careful not to apply reverse voltage to the coil since the snubber diode across the coil will conduct in that polarity.

A photo might help the members provide better advice.

Update... first thank you. for all the information.  I do have sufficient meters to read resistance, DC, AC etc..  I also think I'm reading that I probably need to remove any relays that I want to test.  So I think I should remove the relay in question, apply 12 VDC to the 'input' pins and insure the switch closes??  I'm pretty sure I'm oversimplify something here.

But, I've decided this a long term project .. to understand how this work and how to troubleshoot it.  I know how to do. the soldering, I do quite a bit of photo-etch soldering for models.

Tom

Yes I believe this is correct... if I'm reading the Data Sheet correctly.

Try some resistance measurements before removing components (with the card disconnected from power). It may tell you a lot with a lot less work.

Good plan.  Resistance testing on the PCB is usually complicated by the snubber diodes across the coils.  I default to the Goesinta/Goesouta test.  If the circuit provides power to the relay but the contacts don't transfer - replace it.

Goesinta = Goes in to