Simplex 4004 NAC Issue.

[firefreak57]

@theboginator

First thing I’d do is remove the devices you’re currently using and swap in some known good devices on each NAC, then make sure the EOLs are connected properly, the panel isn’t indicating a NAC fault, and test the system again. If it continues to behave strangely, I’ve listed some additional troubleshooting steps below.

The troubleshooting steps I would do are in this order. If any of these steps fail, stop there and report back. Make sure you disconnect power from the panel before making any kind of electrical connection on it. I’d just leave the batteries disconnected for this since you’ll be constantly plugging in and unplugging the power.

1. Disconnect field wiring and resistors from the FACP then power it up. The panel should indicate NAC trouble.
2. Put the proper type of EOL Resistor across the terminals of both NACs then power the FACP up again. The panel should not indicate any NAC troubles. If it does, remove power, verify the resistors are the correct value and have not been damaged, and check again.
3. Take a known good device from your collection, and connect it to one of the NACs with a temporary length of wire. Strobes and 2-wire horn/strobes should be on a NAC programmed for continuous. Put the EOL resistor after this device. Set the coding to continuous, then power the panel up. If it still indicates normal, initiate an alarm and see if the signal sounds as expected. If it works just fine, try setting coding options and make sure the devices perform properly. Note that strobes typically do not like coded power supplies and should be receiving continuous power.

If steps 1-3 are successful then we can likely rule out panel failure as the cause of your problem and begin focusing on device failure and/or wiring issues.

4. Connect your NACs back up the way you originally had them, 1 NAC at a time. Use known good devices for this test, wire up the entirety of NAC 1 with the EOL resistor at the end. If the panel still indicates normal, initiate an alarm and check that the device works as intended. Once you have verified NAC 1 is working, reconnect devices to NAC 2 with the EOLR at the end of the loop, and test the panel again. If at any time during this process you notice a trouble condition occur, it’s likely you have a wiring issue (i.e. the wire sheath was stripped and the conductor underneath is touching bare metal or the connector of another NAC.
   Again, remove power from the panel prior to connecting wires to it. NACs are designed to withstand direct shorts during supervision (but not alarm), but if you were to accidentally touch 2 separate wires together and backfeed voltage into a NAC you could destroy it. I ruined my first MS-4 this way and a Simplex 4004 is almost certainly more expensive to replace so definitely be careful! Post a reply if you have any luck!

It was the NAC jumpers. NAC 2 has to be on until reset to override the coding from NAC 1.