Trane / ML Series R-410A
Trane UPPER LAMP LIGHTS UP error code
Trane's troubleshooting table lists upper lamp lights up with the outdoor unit not operating as outdoor control system trouble. The manual says the inverter PCB or outdoor PCB cannot read data in nonvolatile memory and directs the technician to check the outdoor board LED pattern.
- Urgency
- advisory
- Verified
- Jul 31, 2026
- Fix path
- Technician
What it means
Trane's troubleshooting table lists upper lamp lights up with the outdoor unit not operating as outdoor control system trouble. The manual says the inverter PCB or outdoor PCB cannot read data in nonvolatile memory and directs the technician to check the outdoor board LED pattern.
Urgency
advisory
Try one safe reset. If the outdoor unit still does not run, schedule service.
Likely causes
- The outdoor unit is not operating while the indoor lamp stays on
- The inverter PCB or outdoor PCB cannot read stored memory data
- The outdoor board LED diagnostic pattern needs technician follow-up
Homeowner fix
Power cycle the system once if you can do that safely. Confirm the outdoor unit has not been switched off at a service disconnect, but do not open the cabinet.
When to call a pro
Call a licensed HVAC technician if the outdoor unit remains off. Tell them Trane maps this steady-lamp condition to outdoor control-system diagnostics.
This code points to electrical or inverter work - get repair quotes from contractors in your area.
Get repair quotesRepair vs replace
Outdoor board repair can be reasonable on a newer system. Compare replacement for an older system if the diagnosis includes multiple outdoor electronics.
See Trane mini-splitsYour Trane model
ML Series R-410A model pages in the Trane catalog help compare this repair path with current replacement options.
For your technician
Technician note: inspect outdoor board LED blink pattern and diagnose inverter PCB/outdoor PCB nonvolatile-memory and control-system faults per Trane service manual. Page context: Trane maps this display to the ML Series R-410A line; source: Trane MyLinkDrive NTXWMT-A111A(B) Service Manual, Section 9 Troubleshooting; display convention: match the letter U, letter P, letter P, letter E, letter R, letter L, letter A, letter M, letter P, letter L, letter I, letter G, letter H, letter T, letter S, letter U, and letter P marker exactly before comparing neighboring codes.
Which systems show it
ML Series R-410A
Related troubleshooting
Use the symptom guide alongside the exact display code if the unit is flashing, cycling, or showing comfort symptoms.
Related codes
Source
- Document
- Trane MyLinkDrive NTXWMT-A111A(B) Service Manual, Section 9 Troubleshooting