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Security & Fire Protection Systems/Alarm sounding randomly for two days on DSC PC1500


QUESTION: We have a DSC PC1500 that is not monitored.  For two days (and all through the night)the alarm would go off periodically and loudly.  It sounds three or four times then stops.  The problem zone says it is Zone 4, Fail to communicate, however the system is NOT monitored and hasn't been in six years.  We do not have the master code.  Could this be the battery?  I'm desperate!!  It's going off again LOUDLY!!!!!!

ANSWER: Hello Cassie, and thanks for writing.

It's too soon to say what the issue is, but at least we can get started. We're going to see if the battery is your problem.

I'd like you get a small screwdriver, and go to the main control panel (this is not the keypad).

Open the panel, and look at the main board inside. There's a terminal strip across the bottom. At the far left terminals 1 and 2 are for AC power. I'd like you to remover the wire from terminal 1. Just loosen the screw and pull it off, being careful not to let it touch anything in the panel. And you need not worry about a shock; it's only 16.5 volts.

What this does is forces your panel to run on the battery only. A good battery will be able to run the system for 4 hours, and then be able to sound the siren at full strength for 5 minutes.

So just wait for an hour or two, and then purposely set off the alarm. to see if the siren works. If it does not, I'm certain the battery needs to be replaced.

The failure to communicate message is a separate problem. We'll deal with that later.

Let me know how the siren test goes.

Best Regards,


---------- FOLLOW-UP ----------

QUESTION: Well.....we replaced the battery (before I got your reply).  The siren did not go off for about three hours and then it started the "random" siren again.  I also did as you suggested above, even though we had replaced the battery.  The alarm did go off with just the new battery for 5 minutes.  

The SYSTEM light is solid.  After a power outage, I have never been able to get it to go off.  (this happened about a month ago but everything was still working.)  

However, I tested with *2 and now it is telling me zone 3 AND 4.  

So.......I'm guessing it's the Bell fuse but have NO IDEA how to deal with that.

Thanks for the new info, Cassie.

I'm afraid that's not good news. The indicator for zone 3 (using the *2 command# is for a thermal fuse #called a PTC or "positive temperature coefficient") that protects the power output to either the siren or other devices powered through the auxiliary output.

I found a reference that notes if the backup battery is connected backwards that it will affect the PTC, but I think this unlikely in your case. But to ensure we leave no stone unturned, please check that you have the correct polarity for your battery connections -- red for positive, black for negative.

And there's one thing to try on your own before having to get a technician on site.

Do a complete power-down and restart. Disconnect the AC and the battery, wait five minutes, then reconnect the battery and AC.

If there's any foul-up in system memory, this will clear it.

If the problem persists after this, you likely need a new motherboard, and you'll need a technician on site for that.

Please let me know what happens!

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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