HVACopediaLennox · Air conditioner
RDS Test button Refrigerant detection board Test button - simulated leak test
What the display is showing
The RDS blower control board (27A02) has a Test/Reset button used at start-up. After power is restored the system runs a 5-minute purge sequence before you test. Pressing Test during a call makes the board act as if a leak was found: its LED flashes blue, the blower starts and the compressor stops (the gas burners also stop on a heat call). Nothing is wrong; it is only a check of the wiring.
Applies to: Lennox EL16KC1 A/C with RDS blower control board 27A02 (R-454B)
What to do
- Restore power and wait for the 5-minute purge to finish.
- Cooling check start a cooling call at the thermostat, press Test on the RDS board, and confirm the LED flashes blue, the blower runs and the outdoor compressor stops.
- Press Test again to end the simulated leak.
- Heating check (gas furnace) start a heat call, press Test, and confirm the blue flashing LED, blower on, burners off and compressor off. Press Test again to end it.
Settings for these units
Outdoor unit clearances · Lennox EL16KC1
| Location | Clearance |
|---|---|
| Service side (one side next to control box) | 30 in. |
| One of the other three sides | 36 in. |
| One of the remaining two sides | 12 in. |
| Last side | 6 in. |
| Between two units | 24 in. |
| Top | 48 in. |
| Above roof surface (roof mount) | 6 in. (152 mm) minimum |
Increase clearances where snow/ice can fall on the unit or air can recirculate.
Wind barrier, if used, 24 in. (610 mm) from the unit.
Models that show this code
9 models in Lennox EL16KC1
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Source: Lennox EL16KC1 (Elite A-C, R-454B) Installation Instructions 100121 (01-2025), Start-Up Test Procedure (RDS Blower Control Board), printed p.35-36. Summarized in our own words; check the original manual for your model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.