E73/E74 wiring problem

[joemcrane]

I just changed out a working thermostat with a nest 3rd generation.  I keep getting an E73 or E74 message depending on which side I put the power cable.  The thermostat can tell where the cable is because if I change it, it shows such in the wiring diagram.

Also, when I set up the app, I made it electric only and didn't choose the gas option which is actually what I have.  I can see this setting in the app but I can't change it.

[Patrick_Caezza · Accepted solution]

@joemcrane 

The E73 and E74 errors mean the R wire is not receiving power. Check your furnace and see it the control board fuse has blown.

[joemcrane]

It was a blown fuse.  Thanks a lot for the help.

[RCoop]

what else could be this issue other than a broken wire?