PLC Relay Output

Hello all....I have an issue with relay output module connected to a compactlogix controller. The output is switching 24vdc to pulse an audible alarm. Every-so-often the alarm sounds constantly while the output is off and no LED on the module. II switched to another output point and the same result. Anyone have an idea why and what I can do to solve this? Thanks...

Wow - ESP works.

The reply I posted in your other post that was empty fits.

Have the PLC output turn on a general purpose relay & use that relay to sound the alarm.

Really though, unless the alarm draws high amps that might cause the output relay contacts to weld together, or it's not actually a relay output that's allowing enough current through in the OFF state to activate the alarm (like a TRIAC) in this condition I add a 100 ohm resistor from the relay output to common to deactivate the device

I even had to do this on a laser projector that was powered by an AC adapter from a TRIAC output, when OFF it built up enough charge in the AC adapter to flash the laser on quickly about every second.

what is the model number of the output card?
If its a relay card, the contacts have a mechanical life span.
Is the relay cycling on / off or does the audible alarm automatically operate?
Is the output protected?
You may want to use a solid state module.

regards,
james