The alarm is telling you that something in your system has failed. To find out what it is you will need to test the system. Unfortunatly with this model furnace there is no easy answer.
The first link will take you through the diagnostics of your unit. The second link is the installation manual for your unit. It may help with the diagnostic proceedure
I wish I could be more help but the only way that I could do that would be to be there doing the diagnostics for you.
If you have any problems just let me know and i will walk you through that part of the testing.
If this has answered your question click the green ACCEPT button.
If you have other concerns in this matter please reply here in this thread.
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Best regards; The Home Smithy