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Back to Trane DHC120HW*(L,M,H,X,Y,Z)A

Trane DHC120HW*(L,M,H,X,Y,Z)A troubleshooting and error codes

Use this table to identify what the visible code may mean and what information to share when scheduling service. Keep checks simple and visible; do not open electrical, refrigerant, gas, or sealed equipment compartments.

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Error-code table

Search codes for DHC120HW*(L,M,H,X,Y,Z)A

Code Meaning System area Safe first step Action
Ignition Off No power or ignition-board failure Precedent gas heat ignition board Record the flash pattern, avoid repeated reset attempts, and schedule GreenFlow service. View details
RTRM LED2 1 Blink Emergency stop open during test mode ReliaTel RTRM controls Record the flash pattern, avoid repeated reset attempts, and schedule GreenFlow service. View details
Ignition Fast Flash Ignition board not communicating with RTRM Precedent gas heat ignition board Record the flash pattern, avoid repeated reset attempts, and schedule GreenFlow service. View details
RTRM LED2 2 Flashes ReliaTel diagnostic present ReliaTel RTRM controls Record the flash pattern, avoid repeated reset attempts, and schedule GreenFlow service. View details
Ignition 2 Flash System lockout from flame-sense failure Precedent gas heat ignition board Record the flash pattern, avoid repeated reset attempts, and schedule GreenFlow service. View details
Service output ON Clogged filter switch active ReliaTel service output Document the flash pattern, check thermostat, filter, and visible outdoor-unit obstruction status, and schedule service if the condition remains. View details
Ignition 3 Flash Pressure switch fault Precedent gas heat ignition board Record the flash pattern, avoid repeated reset attempts, and schedule GreenFlow service. View details
Service output Pulsing Fan, freeze, smoke, or condensate diagnostic ReliaTel service output Record the flash pattern, avoid repeated reset attempts, and schedule GreenFlow service. View details
Cooling output Pulsing Cooling circuit or pressure diagnostic ReliaTel cooling output Record the flash pattern, avoid repeated reset attempts, and schedule GreenFlow service. View details
Ignition 4 Flash High-temperature limit circuit open Precedent gas heat ignition board Record the flash pattern, avoid repeated reset attempts, and schedule GreenFlow service. View details
Heat output Pulsing Heat or gas-heat diagnostic ReliaTel heating output Record the flash pattern, avoid repeated reset attempts, and schedule GreenFlow service. View details
Ignition 5 Flash Flame sensed when gas valve is not energized Precedent gas heat ignition board Record the flash pattern, avoid repeated reset attempts, and schedule GreenFlow service. View details
Heat + Cool Heat-pump sensor, defrost, phase, smoke, Frostat, or communication diagnostic ReliaTel simultaneous fail codes Record the flash pattern, avoid repeated reset attempts, and schedule GreenFlow service. View details
Ignition 6 Flash Flame rollout circuit open Precedent gas heat ignition board Record the flash pattern, avoid repeated reset attempts, and schedule GreenFlow service. View details
Cool + Service Static pressure transducer diagnostic ReliaTel VAV/static pressure controls Record the flash pattern, avoid repeated reset attempts, and schedule GreenFlow service. View details
Ignition 7 Flash W2 call before W1 on electromechanical units Precedent gas heat ignition board Record the flash pattern, avoid repeated reset attempts, and schedule GreenFlow service. View details
Heat + Cool + Service High duct static pressure trip or transducer ground issue ReliaTel VAV/static pressure controls Record the flash pattern, avoid repeated reset attempts, and schedule GreenFlow service. View details

Safety note

What is safe to check before service

These pages are meant to help document the issue, not replace diagnosis. GreenFlow should handle pressure-switch, electrical, refrigerant, lockout, recurring, and warranty-related conditions.

Safe visible checks

  • Thermostat display and settings
  • Filter condition and return-air path
  • Visible outdoor-unit obstruction
  • Photos of the code, unit, and nameplate

Stop and call

  • Repeated lockouts or recurring faults
  • Pressure-switch or sensor faults
  • Electrical odor, unusual noise, or ice buildup
  • Any sealed cabinet, refrigerant, gas, or warranty issue

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Murali S.

HVAC technician was punctual, followed up well, completed quick repairs, ensured the issue was resolved, and provided helpful recommendations.

Neal V.

In an industry that often fraught with contractors taking advantage of homeowners, Andrey was honest with his assessment and willing to install a product acquired elsewhere (most want that margin themselves), patiently answered my questions (I’m an engineer so like to understand what’s happening), and proactively offered practical...

Jahangir R.

They were very organized to communicate and be on time to come to look at my air condition to fix it.

Dev W.

I had a breakdown of my cooling system and Hanna at Green Flow responded to my request right away. They scheduled me same day. The team at Green Flow was easy to communicate with over phone and text. They kept me updated on delays on arrival of the...

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