I am not home at the moment to get you the air exchanger model number, but can provide this evening.The full background is:1) Bought a new Nest thermostat
and installed on my main 5 ton zone.
2) The thermostat worked for a few days
3) The thermostat threw a warning that there is an issue with the yellow wire (cool)
4) In testing the yellow wire at the thermostat, the Nest would work when the multimeter showed the following.
- TEST A = Red lead from meter to red wire, black lead from meter to yellow wire. Reads 28 volts.
5) Currently, TEST A is showing 0 volts at the thermostat.
6) I traced back to the control board for the air exchanger and located the R, Y, G, W and Common posts where the thermostat wires attached.
7) Running TEST A on the actual control board posts is showing 0v.At this point, I feel like I may have a bad relay. Is there any additional information you need? Any ideas?I attached pictures of the control board where I am now performing TEST A and another of the relay model.