Bosch P1 error code

What it means

P1 means high or low voltage protection. In plain English, the outdoor unit detected voltage or current outside the safe operating range.

Urgency

Likely causes

1. Incoming power is too high, too low, or unstable
2. Loose or high-resistance power connection
3. Outdoor board, inverter, or current-sensing circuit fault
4. Compressor or fan load is pulling abnormal current

Homeowner fix

Power cycle once at the breaker or disconnect if you can do that safely. If the code returns, the breaker trips, or other home electrical symptoms appear, leave the system off and call for service.

When to call a pro

Call a licensed HVAC technician if P1 returns after one safe reset or the condition will not clear. Tell them the official source lists P1 as High or low voltage protection.

Repair vs replace

This fault is usually repairable. Replacement is worth comparing only if an older system also needs major board, compressor, or refrigerant-circuit work.

• Bosch Climate 5000 A/B legacy R-410A 9,000 BTU Regular (BMS500-AAU009-1AHWXB / BMS500-AAS009-1CSXRA)

  Climate 5000 A/B legacy R-410A

• Bosch Climate 5000 A/B legacy R-410A 12,000 BTU Regular (BMS500-AAU012-1AHWXB / BMS500-AAS012-1CSXRA)

  Climate 5000 A/B legacy R-410A

• Bosch Climate 5000 Gen 4 R-454B 6,000 BTU Regular (BMS500-AAU006-1AHWXD / BMS500-AAS009-1CSXRD)

  Climate 5000 Gen 4

• Bosch Climate 5000 Gen 4 R-454B 9,000 BTU Max Performance (BMS500-AAU009-1AHWXD / BMS500-AAS009-1CSXHD)

  Climate 5000 Gen 4

For your technician

Technician note: verify line voltage under load, terminals, grounding, DC bus, current sensing, inverter board, reactor/rectifier where applicable, and compressor/fan load. Source: Bosch Climate 5000 G2 A/B IDU service manual Table 14 and ODU service manual Table 12; supporting diagnosis sections where listed; Table 12/Table 14; voltage diagnosis. Page context: Bosch maps this display to the Climate 5000 A/B legacy R-410A line; source: Bosch Home Comfort official Climate 5000 G2/A-B Ductless AC-HP IDU and ODU Service Manuals, wall-mounted error-code tables and diagnosis sections; display convention: match the letter P and one marker exactly before comparing neighboring codes.

Which systems show it

Climate 5000 A/B legacy R-410A

Related troubleshooting

Use the symptom guide alongside the exact display code if the unit is flashing, cycling, or showing comfort symptoms.

Related codes

Source

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