UZC4 - 3rd and fourth stage do not start

[CollertJ]

I have a Bard geothermal furnace with 4 stages of heat - 2 compressor and 2 electric coil heat. With the recent cold snap, our furnace was unable to keep up and I noticed only the first 2 stages were running. I turned off all stats and then back on and waited over an hour and only the 2 compressor stages were running. I switch to emergency heat and the electric coil heat worked. Any ideas on why stage 3 is not starting?

[Paul Z.]

Call 18004463110X490 have a few questions.