Trane · Air conditioner

HL Hard lock: low pressure (LPCO)

Critical severity Trane 5TTR7

What the control is telling you

Low suction pressure reached hard-lock level (fault column says soft-lock). Manual lists only the meaning (A1000BA board); steps are general checks drawn from other sections of the guide.

Applies to: Trane 5TTR7 multi-speed AC (5TTR7024A-060A)

Likely causes

Low charge / leak
Service valve not fully open
Low indoor airflow or iced coil
Restriction

Test and repair steps

Check charge (low charge trips LPCO).
Confirm both service valves are fully open.
Check indoor airflow, filter and indoor coil in cooling; outdoor coil icing in heating.
Check for restrictions in liquid line or drier.

Settings for these units

Outdoor unit placement · Trane 5TTR7

Item	Value
Above unit	5 ft clear
Service side	3 ft
Walls / shrubs	12 in. min
Pad	1 in. larger than unit all round, level, separate from house
Cold climate (HP)	raise 3-12 in. above pad
Within 1 mile of salt water	add BAYSEAC001 if no factory salt shield
Operating range	cooling 55-120 F, heating 0-66 F

Avoid bedroom walls and under roof drip lines.

Dimensions and weights · Trane 5TTR7

Model	H x D x W (in.)	Weight (lb)
5TWR7024A	41 x 30 x 33	181
5TWR7036A	41 x 30 x 33	194
5TWR7048A	41 x 34 x 37	231
5TWR7060A	41 x 34 x 37	241
5TTR7024A	41 x 30 x 33	176
5TTR7036A	41 x 30 x 33	189
5TTR7048A	41 x 34 x 37	226
5TTR7060A	41 x 34 x 37	236

Weights are estimated, uncrated.

Models that show this code

4 models in Trane 5TTR7

5TTR7024A5TTR7036A5TTR7048A5TTR7060A

Other codes on the same units

Fd Discharge temperature sensor fault
HC Hard lock: compressor over-current
HF Hard lock: outdoor fan over-current
HH Hard lock: high pressure (HPCO / DTC)
Hd Hard lock: high discharge temperature
LC Lockout: compressor over-current
LF Lockout: outdoor fan over-current
LH Lockout: high pressure (HPCO / DTC)

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Source: Trane ODR-SVN002E-EN (5TTR7/5TWR7 installer's guide) - section Integrated Variable Speed Control Board LED Indicators, Table 18 (A1000BA models). Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

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.