Security & Fire Protection Systems/False alarm FBI XL-31


I have an unusual problem with intermittent alarming on Zone 9 of this panel. I had previously replaced the exterior siren and strobe which I think had a faulty PCB and would false alarm occasionally. I cannot recall where the previous wiring was, but I have wired the new siren to terminals 18, 19, 20 and programmed Zone 9 for 24hr supervision.  At first I was concerned vermin may have damaged the wiring causing it to fault,  but this circuit should now only supply power to the new siren and of course if damaged the siren will not function.
Could you please point me in the right direction...

Mike Young

ANSWER: Hello Mike, and thanks for your question.

I checked the installation manual for the XL-31; terminals 18-20 are not for the siren. The siren is powered by terminals 3 and 4.

Here's a link to the manual for your panel. The hookup diagram on page 4 should help you get squared away:

Best Regards,


[an error occurred while processing this directive]---------- FOLLOW-UP ----------

Thank you so much for your quick response.

I did another check of the conglomeration of wires and found that the external siren is wired along with three interior sirens through a relay connected to terminal 3(pos), 4(neg) and 5(aux pos). All appears well in that regard.

According to the Manual terminal 19 is Zone 9, the LED that displays when the alarm goes off when not set. Two additional wires from the siren are connected to terminals 19 & 20. The tamper switch has been by-passed so presumably the wires are not for that.....should I remove these wires from the panel and disable zone  9....what do you think...?

Mike Young

Hello Mike, and thanks for checking the siren connections.

If you're sure that zone 9 was for the bypassed tamper alarm, then just put a 2.2k ohm resistor across terminals 19 and 20, and remove those wires. That will prevent an intermittent short or open on the zone wiring from causing a false alarm.

If you're nor sure that zone is for the tamper, consider other things that might be placed on a 24-hour zone -- like glass protection. If you have foil or glass-break detectors, they could be on that zone.

I hope this helps!

Best Regards,


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Dave Neuweiler


The design and application of burglary and fire systems for homes and businesses. Helping alarm owners understand how their system works. Helping to troubleshoot false alarm problems. Questions about monitoring issues.


Over a quarter century in the industry. Experience in installation, service, and monitoring centers. Training manager for a national protective services company; director of education and training for a national trade organization for for alarm dealers.


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