What are the symptoms of Blower vents emit warm air when A/C is turned on in Ford FOCUS IV (HN)?

No cold air from vents. Frost or ice on pipes under the hood

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Blower vents emit warm air when A/C is turned on

Q: How to fix Blower vents emit warm air when A/C is turned on in Ford FOCUS IV (HN)?

The air conditioning becomes completely dead (it only blows hot air, the radiator fan does not spin). Authorized services often incorrectly diagnose the problem as a failure of the fully electric compressor (estimating the repair at approximately EUR 4,000). The real cause is a dashcam connected to the OBD socket, which constantly consumes electricity. The Battery Management System (BMS) detects a drop in voltage and intentionally permanently cuts off power to the powerful air conditioning compressor, protecting the battery. Solution: Disconnecting the external accessory from the OBD port (allowing the BMS to reset the status) and, in this diagnosed case, replacing the faulty gas pressure sensor.

in Ford FOCUS IV (HN) (2021-2021)

Symptoms

No cold air from vents
Frost or ice on pipes under the hood

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Technical diagnosis (Premium)

Recognized technical fault:

Auxiliary controller voltage instability detected

Technical analysis

Detailed analysis of HVAC controller operation parameters, CAN bus data readings, and diagnostic signal waveforms. Purchase PRO access or log in to read the full fault analysis.

Confirmed solution

Complete step-by-step repair procedure including module non-volatile memory reset, sensor calibration, and correct wiring routing. Unlock the full report to see the instruction.

Parts needed

Filters ferrite anti-interference / noise suppressor
Auxiliary starting battery (depending on cell status)

Workshop hacks

Important workshop tips for mechanics regarding bypasses without expensive control module replacement and manufacturer software service bulletins.

TSB / TPI service bulletins

TSB-24-HVAC-01TPI-2068943/2

A/C Technical Specifications

IV - (DEH)

Refrigerant: R1234yf Amount (g): 430-480g Oil: PAG YF ISO 46 Oil (ml): 120 - 140ml

IV 1,0 i EcoBoost/1,5 TDCi/1,6 TDCi

Refrigerant: R1234yf Amount (g): 530g Oil: WSS-M2C300-A2 PAO 68 AA1 lub PAG ISO 46 YF Oil (ml): 130ml

IV 1,5 i EcoBoost/2,0 TDCi

Refrigerant: R1234yf Amount (g): 625g Oil: WSS-M2C300-A2 PAO 68 AA1 lub PAG ISO 46 YF Oil (ml): 110ml

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Blower vents emit warm air when A/C is turned on

Symptoms

A/C Technical Specifications

Other problems in FOCUS IV (HN)

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