Nordyne (1994 vintage?)
Heating Coils: E1EH-202HA
Split System Heat Pump: no info on tag
A/C Coil: C1QA-042U-B
Heat/Cool Blower: 902805
A/C system worked fine this past summer (2008).
Heat worked until about 3 weeks ago. My Mother awoke to a cold house. Ducts were blowing cold air. T-stat was set for "Heat". She set to "E-heat" and that worked to warm the house.
I found breakers to outside Heat Pump tripped. Reset breakers. Called for normal "Heat", breakers tripped. Shut off all breakers, re-seated all electrical connections (I could find) and tightened all terminal screws. Breakers back on, call for heat, Heat Pump breakers tripped again.
Waited 15 min. Set T-stat to "Cool" (to narrow problem to heat and/or cool). Set temp to turn on, A/C breakers to Heat Pump tripped.
May 2007: Serviceman replaced a "3C114 WR Sequencer" and added R-22.
I'm still reading the posts for similar situations...
p.s. I also saw your comment about placing filter on door vent. This installation has air handler in same closet (about 5'x2') as water heater. I'm not sure if there is a filter location under the A-coil. Your recommended filter location: Door, top of A-Coil, under A-Coil (if available)?
"Humbly Grateful" for you advice,