Lennox SLP98UHV Error Code E 349: No 24V Between R and O
What Does Code E 349 Mean?
Error code E349 on the Lennox SLP98UHV indicates that there is no 24 volts present between the R and O terminals on the control board in non-communicating mode. This typically means a factory-installed jumper link between R and O has been cut or removed.
The R-to-O connection is required for proper heat pump reversing valve operation in non-communicating setups. When this link is missing, the system may experience a voltage brownout condition, and the heat pump reversing valve will not receive the proper signal to switch between heating and cooling modes.
This is a configuration issue rather than a component failure. During installation, service work, or thermostat wiring changes, a technician may have inadvertently cut or removed the R-to-O jumper link. Restoring the connection by hard-wiring the R to O terminals on the terminal strip should resolve the code.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| R to O jumper link was cut or removed during installation or service | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- Your heat pump is not switching between heating and cooling modes properly
- The code appeared after recent installation or wiring work
- You also see low-voltage related error codes
✓ Verified against manufacturer service manual — March 2026