White Rodgers Tstat 1F82-51 - Malfunction

The Malfunction light on the thermostat is blinking. When I first noted this, the airhandler was running, but am unsure if the heatpump was working (a 12 yr old Trane XL 1200). The hp now just makes a clicking sound.
Of course, I am hoping this is something simple, (possibly related to the Tstat?) that I might repair. Of course, given the age of the unit this may just be wishful thinking. Any ideas on a possible cause/solution?
Thank you.
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Gopack, Just looked at the technician's factory service manual for a Trane XL 12 and I have a very good idea what your problem is. However, before I confirm a couple of things I need to know about your heating and air conditioning system to come up with the solution for your problem, I just want to ask you one question first. What kind of car do you drive? I drive a piece-of-shit work truck and I just want to compare my shit-mobile to your fine vehicle first.
Jabs

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