Bosch Compress A01-5378 fault code Bosch Compress heat pumps
Share this page What it means Outdoor unit defrost failure
The outdoor unit could not complete a defrost. Bosch's listed causes are heating-side, not refrigerant-side — the system could not supply enough heat to defrost with.
UK models this code applies to From the Bosch service literature we hold (Worcester Bosch user interface HPC 410 manual 6721832682 (2021/02) §8 Unit troubleshooting, Table 38) — not a scraped list.
Compress 3400i AWS 4 kW (CS3400iAWS 4 OR-S) Compress 3400i AWS 6 kW (CS3400iAWS 6 OR-S) Compress 3400i AWS 8 kW (CS3400iAWS 8 OR-S) Compress 3400i AWS 10 kW (CS3400iAWS 10 OR-S) Compress 5800i AW 4 kW (CS5800i AW 4 OR-S) Compress 5800i AW 5 kW (CS5800i AW 5 OR-S) Compress 5800i AW 7 kW (CS5800i AW 7 OR-S) Compress 7001i AW 5 kW (CS7001iAW 5 OR-S) Compress 7001i AW 7 kW (CS7001iAW 7 OR-S) Compress 7001i AW 9 kW (CS7001iAW 9 OR-S) Compress 7001i AW 13 kW (CS7001iAW 13 OR-S) Compress 7001i AW 17 kW 3-phase (CS7001iAW 17 OR-T) Greensource 6 kW (air to water) Greensource 7 kW (air to water) Greensource 9.5 kW (air to water) Compress 7000i AW CS7000i AW 5 OR-S Compress 7000i AW CS7000i AW 7 OR-S Compress 7000i AW CS7000i AW 9 OR-S Compress 7000i AW CS7000i AW 13 OR-S Compress 2000 AWF 4 R-S (CS2000AWF 4 R-S) Compress 2000 AWF 6 R-S (CS2000AWF 6 R-S) Compress 2000 AWF 8 R-S (CS2000AWF 8 R-S) Compress 2000 AWF 10 R-S (CS2000AWF 10 R-S) Compress 2000 AWF 12 R-S (CS2000AWF 12 R-S) Compress 2000 AWF 14 R-S (CS2000AWF 14 R-S) Compress 2000 AWF 16 R-S (CS2000AWF 16 R-S) Compress 2000 AWF 12 R-T 3-phase (CS2000AWF 12 R-T) Compress 2000 AWF 14 R-T 3-phase (CS2000AWF 14 R-T) Compress 2000 AWF 16 R-T 3-phase (CS2000AWF 16 R-T) Compress 2000 AWF 18 R-T 3-phase (CS2000AWF 18 R-T) Compress 2000 AWF 22 R-T 3-phase (CS2000AWF 22 R-T) Compress 2000 AWF 26 R-T 3-phase (CS2000AWF 26 R-T) Compress 2000 AWF 30 R-T 3-phase (CS2000AWF 30 R-T) Compress 6000 AW Compress 6000 AW-5 Compress 6000 AW Compress 6000 AW-7 Compress 6000 AW Compress 6000 AW-9 Compress 6000 AW Compress 6000 AW-13t Compress 6000 AW Compress 6000 AW-17t Compress 3000 AWS — ODU 7.5s (8 kW, single-phase) Compress 3000 AWS — ODU 10s (11 kW, single-phase) Compress 3000 AWS — ODU 11s (14 kW, single-phase) Compress 3000 AWS — ODU 12s (16 kW, single-phase) Compress 3000 AWS — ODU 11t (14 kW, 3-phase) Compress 3000 AWS — ODU 12t (16 kW, 3-phase) Compress 3000 AWS ODU Split 2 Compress 3000 AWS ODU Split 4 Compress 3000 AWS ODU Split 6 Compress 3000 AWS ODU Split 8 Compress 3000 AWS ODU Split 11s Compress 3000 AWS ODU Split 13s Compress 3000 AWS ODU Split 15s Compress 3000 AWS ODU Split 11t Compress 3000 AWS ODU Split 13t Compress 3000 AWS ODU Split 15t
Now the harder half: proving what caused it A01-5378 names a symptom, not a root cause. In the app, the same code opens a guided investigation: what to measure first, the expected values for your exact model, and an honest verdict — including “nothing in this machine is broken” when that's what the readings say.
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