If the LN card has a steady heartbeat it's probably ok. Rapid rate indicates LON trouble....somewhere.
The L24 cards are easily replaced.
On a side note, there have been times I've checked Fire recall only to find after switching back to "off", the hall calls didn't come back on. Turning the fire service key to on/off or bypass restored hall risers. This is on earlier TAC20's with the 2389 keys.
