Payne py3pna042090ab

Unit has no readout on thermostat.checked 24v at unit=good.continuity on green and red wires are good from unit to thermostat.no voltage coming back from thermostat to unit. This should be a bad thermostat but wanted some confirmation.also,I pushed contactor to make unit work and the only thing that came on was the compressor.could I have multiple problems or will the thermostat cause the blower motor not to come on?

Do you have a common wire (not the red one) at the thermostat for power or just battery power?

Should read 24v between the red and common at thermostat.
Contactor = compressor and condenser fan motor only (for the most part)

Blower on green wire

Package or split system?
straight cool with gas heat or heat pump?

I bet you just need to change the batteries in the thermostat.