I recently added the c wire, and I started getting the error e159. Before that my unit would work fine but occasionally would go offline for low battery. I decide to add the c wire to correct that however I get the e159 code which indicate no power to common (C). I took a voltmeter and it read 28 volt at the thermostat between the red and the common wire.
Please help or advise
Thanks for reaching out. Let's see what's going on — what's the make and model of your HVAC system? Do you have a heat pump? If so, the wire in the C terminal may be the changeover valve wire, or you may have a 2-wire changeover system. Also, try reinserting the C wire to see if that helps.
Just checking in to make sure that you've seen our responses. Please let me know if you have other questions or concerns as I will be locking this in 24 hours if I won't hear back from you again. Feel free to start a new thread and we'll be happy to help.