Applicable Systems
S30 Thermostat
EL280 Furnace
XC21 Condenser
Merit Series
Symptoms
Outdoor temperature sensor reading abnormal; thermostat may not optimize heating/cooling switch-over; efficiency reduced.
Possible Causes
- Outdoor sensor exposed to direct sun (wrong placement)
- Sensor wiring damaged by weather/animals
- Sensor internal failure from moisture
Troubleshooting Steps
- Step 1: Check outdoor sensor placement (north side, shaded)
Sensor properly shaded - Step 2: Inspect sensor wiring for outdoor damage
Wiring intact, no chew marks - Step 3: Check sensor resistance vs outdoor temp chart
Resistance matches chart - Step 4: Replace sensor if resistance out of spec
New sensor reading accurate - Step 5: Clear code and verify outdoor temp reading
Reading matches local weather data
How to Reset
Clear via thermostat diagnostics menu after sensor service.
Common Replacement Parts
- Lennox Outdoor Temperature Sensor P/N: 1032-R
Frequently Asked Questions
- Q: Where to place outdoor temp sensor?
North side of building, under eave, away from vents/exhausts. Must be shaded and at least 5 feet above ground.
Source: Lennox S30 Installation Manual
Category: HVAC Residential