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Bosch · Heat pump

o37 Low refrigerant in heating

High severity Bosch IDS Light

What the control is telling you

The unit detected too little refrigerant in heating mode.

Applies to: Bosch IDS Light BOVA15 (24/36/60) R-454B heat pump outdoor units

Likely causes

  • Closed service valves
  • Damaged refrigerant lines
  • Failed transducer or T4/T5 sensor
  • Undercharge

Test and repair steps

  1. Open the service valves.
  2. Check for damaged lines.
  3. Check the pressure transducer and T4/T5 sensors.
  4. Charge the system correctly.

Models that show this code

3 models in Bosch IDS Light

BOVA15-24BOVA15-36BOVA15-60

Other codes on the same units

  • F42 Low pressure sensor fault
  • H01 Drive chip communication fault
  • J00-JCF Compressor driver fault
  • n00-nCF Outdoor fan motor driver fault
  • P0 Control board / compressor IPM overheating
  • P1 High pressure protection
  • P4 High compressor discharge temperature
  • P5 Condenser coil temperature protection (cooling)

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Source: Bosch IDS Light installation BTC 762003308 D (02.2025), Fault Code Table 23 and 17.12 Error Code Troubleshooting, p.42-59. 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.