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York · YZF42B21S LX Series AC

York YZF42B21S LX Series AC EF Error Fix: Outdoor Unit Fan Speed Sensor Error

The fan speed sensor in the outdoor unit is malfunctioning or disconnected, causing improper fan speed detection and potential system faults.

Medium severity2 fixes available

Quick Answer

Error EF on the York YZF42B21S LX Series AC means: Outdoor Unit Fan Speed Sensor Error. The top-ranked community fix is “Replace Fan Speed Sensor” (hard difficulty, ~45 min, DIY cost: $30-$50). 2 community-ranked fixes available below.

Published February 2026 · 2 fixes · air conditioner

Content is based on manufacturer service documentation, community repair experience, and OEM technical bulletins. Always verify with your owner's manual.Learn about our editorial standards.

Root Cause Analysis

Sensor MalfunctionPrimary

Electrical Fault → Wiring Harness Damaged

When to Call a Professional

While many air conditioner repairs can be done safely at home, consider hiring a qualified technician if:

The repair involves electrical wiring, gas lines, or refrigerant
You've tried the top-ranked fix and the error persists
You smell gas, see sparking, or notice water leaking
The repair requires specialized tools you don't have
Your appliance is still under manufacturer warranty

Average professional repair cost for this issue: $160-$220.

Other York Models with Error EF

DERA-F036N07 14 SEER

air_conditioner · 2 fixes

Other York YZF42B21S LX Series AC Error Codes

Indoor Temperature Sensor Failure

2 fixes

Outdoor Coil Temperature Sensor Fault

2 fixes

High Pressure Switch Trip

2 fixes

Low Pressure Switch Trip

2 fixes

Compressor Overcurrent Protection

2 fixes

Indoor Fan Motor Locked Rotor

2 fixes

Outdoor Fan Motor Locked Rotor

2 fixes

Indoor Coil Freeze Protection Activated

2 fixes

People Also Ask About York YZF42B21S LX Series AC Error EF

What does error code EF mean on a York YZF42B21S LX Series AC?

Error code EF on the York YZF42B21S LX Series AC means: Outdoor Unit Fan Speed Sensor Error. The fan speed sensor in the outdoor unit is malfunctioning or disconnected, causing improper fan speed detection and potential system faults.

How do I fix error code EF on my York YZF42B21S LX Series AC?

The most successful fix is "Replace Fan Speed Sensor" (hard difficulty, ~45 minutes). Estimated DIY cost: $30-$50. HomeMD has 2 community-ranked fixes for this error.

Is error code EF on a York YZF42B21S LX Series AC serious?

This error is rated medium severity. It should be addressed soon, but your appliance may still function in a limited capacity.

Can I fix York YZF42B21S LX Series AC error EF myself?

Yes — the top-ranked community fix ("Replace Fan Speed Sensor") is rated hard difficulty and takes about 45 minutes. Tools needed: Phillips screwdriver, Multimeter.

How much does it cost to repair York YZF42B21S LX Series AC error EF?

DIY cost: $30-$50. Professional repair typically costs $160-$220. Many homeowners save money by trying the top-ranked community fix first.

What other error codes does the York YZF42B21S LX Series AC have?

The York YZF42B21S LX Series AC has 8 other known error codes, including: E1 (Indoor Temperature Sensor Failure), E2 (Outdoor Coil Temperature Sensor Fault), E3 (High Pressure Switch Trip), E4 (Low Pressure Switch Trip), E5 (Compressor Overcurrent Protection), and 3 more.

Which other York models have the EF error?

Error code EF also appears on 1 other York model: DERA-F036N07 14 SEER. The fix may vary by model, so check each model's specific page for tailored repair steps.

What other error codes does the York YZF42B21S LX Series AC have?

The York YZF42B21S LX Series AC has 8 other known error codes:

E1 — Indoor Temperature Sensor Failure (2 fixes)
E2 — Outdoor Coil Temperature Sensor Fault (2 fixes)
E3 — High Pressure Switch Trip (2 fixes)
E4 — Low Pressure Switch Trip (2 fixes)
E5 — Compressor Overcurrent Protection (2 fixes)
E6 — Indoor Fan Motor Locked Rotor (2 fixes)
E7 — Outdoor Fan Motor Locked Rotor (2 fixes)
E8 — Indoor Coil Freeze Protection Activated (2 fixes)

Which other York models have the EF error?

Error code EF also appears on 1 other York model:

DERA-F036N07 14 SEER (air conditioner) · 2 fixes

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