🌡️Thermostat

B01

Nest · Nest Thermostat (2020)

Nest Nest Thermostat (2020) B01 Error Fix: Short Cycling (Rapid On/Off)

HVAC system turns on and off repeatedly, running for only a few minutes before shutting down and restarting. Can be caused by an oversized HVAC system, dirty air filter restricting airflow, low refrigerant in the AC system, thermostat placed in a drafty location or near a heat source, or a faulty flame sensor in the furnace. Check and replace the air filter first — this is the most common cause. If short cycling continues, have an HVAC technician check refrigerant levels and system sizing.

High severity2 fixes available

Quick Answer

Error B01 on the Nest Nest Thermostat (2020) means: Short Cycling (Rapid On/Off). The top-ranked community fix is “Inspect and Service HVAC Components to Address Short Cycling” (hard difficulty, ~90 min, DIY cost: $0-$50). 2 community-ranked fixes available below.

Published February 2026 · 2 fixes · thermostat

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.

When to Call a Professional

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

This is a high severity error — continued use may cause damage or a safety hazard
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: $150-$300.

Other Nest Models with Error B01

Nest Learning Thermostat (3rd Gen)

thermostat · 2 fixes

Nest Learning Thermostat (4th Gen)

thermostat · 2 fixes

Nest Thermostat E

thermostat · 2 fixes

Other Nest Nest Thermostat (2020) Error Codes

A01

No Power / Low Battery

2 fixes

A02

'Delayed' Message on Display

2 fixes

A03

No Power to Rh/Rc Wire

2 fixes

A04

W1/W2 Heating Wire Not Detected

2 fixes

A05

Y1/Y2 Cooling Wire Not Detected

2 fixes

A06

G (Fan) Wire Not Detected

2 fixes

A07

O/B (Heat Pump Reversing Valve) Wire Not Detected

2 fixes

A08

Wiring Error / Incompatible Wiring

2 fixes

People Also Ask About Nest Nest Thermostat (2020) Error B01

What does error code B01 mean on a Nest Nest Thermostat (2020)?

Error code B01 on the Nest Nest Thermostat (2020) means: Short Cycling (Rapid On/Off). HVAC system turns on and off repeatedly, running for only a few minutes before shutting down and restarting. Can be caused by an oversized HVAC system, dirty air filter restricting airflow, low refrigerant in the AC system, thermostat placed in a drafty location or near a heat source, or a faulty flame sensor in the furnace. Check and replace the air filter first — this is the most common cause. If short cycling continues, have an HVAC technician check refrigerant levels and system sizing.

How do I fix error code B01 on my Nest Nest Thermostat (2020)?

The most successful fix is "Inspect and Service HVAC Components to Address Short Cycling" (hard difficulty, ~90 minutes). Estimated DIY cost: $0-$50. HomeMD has 2 community-ranked fixes for this error.

Is error code B01 on a Nest Nest Thermostat (2020) serious?

This error is rated high severity. You should address it promptly — continued use could cause damage or safety concerns.

Can I fix Nest Nest Thermostat (2020) error B01 myself?

Yes — the top-ranked community fix ("Inspect and Service HVAC Components to Address Short Cycling") is rated hard difficulty and takes about 90 minutes. Tools needed: T20 Torx screwdriver, Multimeter, Steel wool pad.

How much does it cost to repair Nest Nest Thermostat (2020) error B01?

DIY cost: $0-$50. Professional repair typically costs $150-$300. Many homeowners save money by trying the top-ranked community fix first.

What other error codes does the Nest Nest Thermostat (2020) have?

The Nest Nest Thermostat (2020) has 8 other known error codes, including: A01 (No Power / Low Battery), A02 ('Delayed' Message on Display), A03 (No Power to Rh/Rc Wire), A04 (W1/W2 Heating Wire Not Detected), A05 (Y1/Y2 Cooling Wire Not Detected), and 3 more.

Which other Nest models have the B01 error?

Error code B01 also appears on 3 other Nest models: Nest Learning Thermostat (3rd Gen), Nest Learning Thermostat (4th Gen), Nest Thermostat E. The fix may vary by model, so check each model's specific page for tailored repair steps.

What other error codes does the Nest Nest Thermostat (2020) have?

The Nest Nest Thermostat (2020) has 8 other known error codes:

A01 — No Power / Low Battery (2 fixes)
A02 — 'Delayed' Message on Display (2 fixes)
A03 — No Power to Rh/Rc Wire (2 fixes)
A04 — W1/W2 Heating Wire Not Detected (2 fixes)
A05 — Y1/Y2 Cooling Wire Not Detected (2 fixes)
A06 — G (Fan) Wire Not Detected (2 fixes)
A07 — O/B (Heat Pump Reversing Valve) Wire Not Detected (2 fixes)
A08 — Wiring Error / Incompatible Wiring (2 fixes)

Which other Nest models have the B01 error?

Error code B01 also appears on 3 other Nest models:

Nest Learning Thermostat (3rd Gen) (thermostat) · 2 fixes
Nest Learning Thermostat (4th Gen) (thermostat) · 2 fixes
Nest Thermostat E (thermostat) · 2 fixes

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