Summary

This procedure upgrades/reworks LATL outdoor units by relocating the high-voltage lead on the controller PCB, refreshing thermal interface on the TR PCB, and updating the outdoor control software with a ROM writer. Steps below mirror the photo guide (pp. 1–12).

Applies to

  • LATL outdoor units requiring the controller/TR PCB rework and ROM update

Safety and tools

Safety: Isolate mains, lock-out/tag-out, and allow DC bus to fully discharge before touching any PCB. Use ESD precautions.
Tools/parts: Phillips screwdriver set, ROM writer (FM-ONE or equivalent) with LATL program, thermal paste, alcohol wipes, cable ties, side cutters.

Procedure

1) Access the control compartment (p.2)

  • Remove the front covers to expose the electrical panel and controller. Confirm isolation before proceeding.

2) Remove TR PCB and refresh thermal interface (pp.3–4)

  • Label and disconnect all TR PCB harnesses; remove the TR PCB.

  • Clean the heat-sink/contact area; apply fresh thermal paste to the power device as shown, ensuring full, even coverage (p.4). Refit and reconnect the TR PCB.

3) Unplug and reroute the high-voltage lead on the Controller PCB (pp.5–6)

  • Unplug the high-voltage (HV) connector from the controller PCB (p.5).

  • Reroute the HV cable across the top edge of the PCB as illustrated (p.6).

  • Fit the ferrite and secure the harness with cable ties in the shown positions to maintain clearance and reduce noise coupling (p.6).

4) Program the outdoor control (pp.7–11)

Connect ROM writer (p.7):

  • With power OFF and DC discharged, plug the ROM writer lead into CN5 (flash connector) on the main PCB.

  • Restore power to the unit; the ROM writer powers up from the outdoor unit (p.8).

Select software (p.9):

  • On the ROM writer screen, select folder 212C_A71. If another folder is shown, use ▲/▼ to choose 212C_A71, then press WRITE/OK.

Execute writing (p.10):

  • When prompted to execute, select YES and press WRITE/OK.

Completion (p.11):

  • Wait while “… ” displays during programming.

  • When Complete appears and you are asked to execute again, select NO and press WRITE/OK.

5) Finalise (p.12)

  • Isolate power; wait for DC discharge.

  • Disconnect the ROM writer from CN5.

  • Restore power and test operation (cooling/heating start, fans, error-free status). Refit all covers.

Acceptance checklist (attach to job card)

  •  Covers removed/reinstalled without damage

  •  TR PCB thermal paste renewed and PCB re-seated

  • HV lead rerouted, ferrite installed, and cable ties secured per photo guide

  • ROM writer connected to CN5, program 212C_A71 written, completion confirmed

  •  Power cycled; unit operates normally; no error codes present

  •  Photos taken of reroute and ROM writer completion screen (optional)

Notes & tips

  • Do not over-apply thermal paste—aim for a thin, continuous film.

  • Keep the HV harness clear of inductors and heat-sinks as shown to minimise electrical noise.

  • If the ROM writer does not power, recheck outdoor supply and CN5 seating.

Source: LATL Upgrade – Quick Process Guide (photo steps pp. 1–12).