If Nest detects a problem with the wires connected to its base, you'll see a wiring error during set up.
During setup, Nest will detect the wires that are connected to its base and configure its software for your type of system. If Nest finds a problem during wire detection, a red dot will appear on the screen over the image of the wire connector. Press the ring to see the error message. Messages with an "E" code are errors, messages with an "N" code are notes. Wiring errors must be resolved before Nest can continue setup, but wiring notes do not.
If you are experiencing a wiring error on your Nest, visit our online troubleshooting assistant
Below are descriptions of Nest's wiring errors and notes:
Wiring Errors
| Error | Description | What's going on |
| E1 |
Common wire required. Nest may need a common wire to control your system properly. |
This wiring error may appear after installation if Nest can’t draw power while the heating and cooling system is turned on. This issue can often be solved by updating Nest to the latest software version |
| E2 |
No power wires detected. Rh or Rc wire is required. |
This wiring error will appear if no R, Rh or Rc wire is installed, or if the R, Rh or Rc wire isn’t powered. If you see this error, first verify that power is turned on to your heating and cooling system. If that doesn’t resolve the issue, try reseating the R, Rh or Rc wire(s) you have installed. |
| E3 |
Power wire Rc detected. No connection to equipment present. |
This wiring error will appear if you’ve installed both an Rh and an Rc wire, and the Rc wire doesn’t seem to be live. Either the transformer connected to the cooling system doesn’t have power or the Rc wire isn't hooked up to your equipment. Note: You should only connect both an Rh and an Rc wire when the heating and cooling system has two separate transformers, one for heating and one for cooling. If these systems share a transformer, just insert one R wire into either connector. No jumpers needed. |
| E4 |
Power wire Rh detected. No connection to equipment present. |
This wiring error will appear if Nest doesn't detect any power to the system. If you see this error, first verify that power is turned on in to your heating and cooling system and that the fuse or circuit breaker is in good shape. If that isn’t the problem, continue to troubleshoot power issues with your heating and cooling system. |
| E5 |
No heating or cooling wires detected. W1 or Y1 wire is required |
This wiring error will appear if Nest cannot detect any wires inserted into W1 or Y1. At least one of these is required. Check the wiring and make sure that the wire tips are straight and fully inserted into the connectors. |
| E6 |
Too many wires detected. Please remove at least one of O/B, W1, Y1 or AUX. |
This wiring error will appear if the wiring combination you’ve installed is illegal. Verify the actual wiring for the system and remove wires from Nest as appropriate. |
| E7 |
O/B wire but no Y1 wire detected. You must connect a Y1 wire if you connect an O/B wire. |
This wiring error will appear if there's an O/B wire connected, but no Y1. If you have a heat pump, you need a Y1 wire. Check the wiring and make sure that you have all wires connected as needed, and that the wire tips are straight and fully inserted into the connectors. |
| E8 |
Stage two heat wire AUX/W2 detected by itself. You must also connect a W1 wire or both O/B and Y1 wires. |
This wiring error will appear if Nest detects a wire in AUX/W2, but no wire in W1 (if it’s a conventional system) or no wires in O/B and Y1 (if it’s a heat pump system). Check the wiring and make sure that you have all wires connected as needed, and that the wire tips are straight and fully inserted into the connectors. |
| E9 |
Common wire (C) detected. No connection to equipment detected. |
This wiring error will appear if Nest detects that there’s a wire inserted into the common wire “C” connector, but there's no power to this wire. You cannot finish setup until you either:
|
| E10 |
Cooling wire Y1 detected. No connection to equipment detected and no power wire C. |
This wiring error will appear if Nest detects that there’s a wire inserted into the Y1 connector, but this wire doesn't have power. For a few systems, this might be normal. Check the wiring and make sure that all wires are connected as needed, and that the wire tips are straight and fully inserted into the connectors. If this doesn’t resolve the issue, your system requires a common wire to be compatible with Nest. |
| E11 |
Heat pump wire O/B detected. No heat pump system present. |
This wiring error will appear if Nest detects that there’s a wire inserted into the O/B connector, but this wire doesn't have power. Check the wiring and make sure that you have all wires connected as needed, and that the wire tips are straight and fully inserted into the connectors. |
| N1 |
Power wire Rc detected. No connection to equipment detected. |
This wiring note will appear if Nest detects that there’s a wire inserted into the Rc connector, but this wire doesn't have power. Check the wiring and make sure that you have all wires connected as needed, and that the wire tips are straight and fully inserted into the connectors. |
| N2 |
Power wire Rh detected. No connection to equipment detected. |
This wiring note will appear if Nest detects that a wire is inserted into the Rc or Rh connector and that this wire doesn't have power. Check the wiring and make sure that you have all wires connected as needed, and that the wire tips are straight and fully inserted into the connectors. |
| N3 |
Heating wire W1 detected. No heating system present. |
This wiring note will appear if Nest detects that there’s a wire inserted into the W1 connector, but there's no voltage on the wire. Check the wiring and make sure that you have all wires connected as needed, and that the wire tips are straight and fully inserted into the connectors. For a few systems, this might be normal. |
| N4 |
Cooling wire Y1 detected. No cooling system present. |
This wiring note will appear if Nest detects that there is a wire inserted into the Y1 connector, but there's no voltage on the wire.
Check the wiring and make sure that you have all wires connected as needed, and that the wire tips are straight and fully inserted into the connectors. |
| N5 |
Stage two heat wire AUX/W2 detected. No auxiliary heating system present. |
This wiring note will appear if Nest detects that there is a wire inserted into the AUX/W2 connector, but there's no voltage on the wire. Check the wiring and make sure that you have all wires connected as needed, and that the wire tips are straight and fully inserted into the connectors. For a few systems, this might be normal. |
| N6 |
Fan wire G detected. No fan present. |
This wiring note will appear if Nest detects that there is a wire inserted into the G connector, but there's no voltage on the wire. Check the wiring and make sure that you have all wires connected as needed, and that the wire tips are straight and fully inserted into the connectors. It may be that this is just the way this system works and there may be nothing wrong. |
Note: Nest uses the connected wires to configure its software for your system and to keep its battery charged. Therefore, if you have wires that aren't connected to power or to equipment, you shouldn't connect these wires to Nest. For example, If you don’t have an air-conditioner and you see error E5, disconnect the wire from Y1 (Y1 is the cooling wire).
Related to...
- Nest Learning Thermostat