Trane · Heat pump

Fr No 24 VAC R signal at outdoor control (heat pump)

High severity Trane 5TWR7

What the control is telling you

The heat pump outdoor control is not getting 24 VAC on R. Heat pumps need both R and O wired to the outdoor unit.

Applies to: Trane 5TWR7 multi-speed heat pump (5TWR7024A-060A)

Likely causes

R wire open or not connected
Indoor transformer/fuse problem

Test and repair steps

Heat pump needs R and O wired to the outdoor unit; check the R wire from the indoor unit.
Measure 24 VAC between R and B at the outdoor control.
Repair the open thermostat/control wire.

Settings for these units

Outdoor unit placement · Trane 5TWR7

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 5TWR7

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 5TWR7

5TWR7024A5TWR7036A5TWR7048A5TWR7060A

Other codes on the same units

L8 Lockout: high coil temperature
FA Outdoor ambient sensor fault
FC Coil temperature sensor fault
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)
HL Hard lock: low pressure (LPCO)

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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.