🌡️Thermostat

FILTER-REMIND

Honeywell · TH4210U2002 PRO 4000 5-2 Day Programmable Thermostat

Honeywell TH4210U2002 PRO 4000 5-2 Day Programmable Thermostat FILTER-REMIND Error Fix: "Filter" Reminder Displayed

The thermostat is displaying a filter change reminder that was configured in the settings — this is a time-based countdown (not measured by actual filter condition) and means the programmed interval has elapsed; reset the reminder after replacing the HVAC air filter: on most models, go to Preferences or Settings and reset the Filter timer to restart the countdown

Medium severity2 fixes available✨ Free fix available

Quick Answer

Error FILTER-REMIND on the Honeywell TH4210U2002 PRO 4000 5-2 Day Programmable Thermostat means: "Filter" Reminder Displayed. The top-ranked community fix is “Replace HVAC Air Filter and Verify Thermostat Reminder Reset” (medium difficulty, ~30 min, DIY cost: $15-$30). 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:

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: $100-$180.

Other Honeywell Models with Error FILTER-REMIND

RTH7600D 7-Day Programmable Thermostat with Backlit Display

thermostat · 2 fixes

RTH9585WF Wi-Fi Color Touchscreen 7-Day Programmable Thermostat

thermostat · 2 fixes

T10 Pro Smart Thermostat with RedLINK Room Sensor

thermostat · 2 fixes

T6 Pro Programmable Thermostat (TH6320WF / TH6220U)

thermostat · 2 fixes

T9 Smart Thermostat with Smart Room Sensor

thermostat · 2 fixes

TH6220D1028 FocusPRO 6000 2H/2C Programmable Thermostat

thermostat · 2 fixes

TH8321WF1001 VisionPRO 8000 Wi-Fi Programmable Touchscreen Thermostat

thermostat · 2 fixes

Other Honeywell TH4210U2002 PRO 4000 5-2 Day Programmable Thermostat Error Codes

APP-OFFLINE

Thermostat Shows Offline in App

"Aux Heat" Displayed

Blank/Dead Display — No Power

2 fixes

BLOWN-FUSE

HVAC Control Board Fuse Blown

2 fixes

COOL-ON-FLASH

"Cool On" Flashing on Display

2 fixes

EM-HEAT

"Em Heat" or Emergency Heat Mode

2 fixes

ERR

"Err" Displayed on Screen

2 fixes

FAN-WONT-STOP

Fan Running Constantly

2 fixes

People Also Ask About Honeywell TH4210U2002 PRO 4000 5-2 Day Programmable Thermostat Error FILTER-REMIND

What does error code FILTER-REMIND mean on a Honeywell TH4210U2002 PRO 4000 5-2 Day Programmable Thermostat?

Error code FILTER-REMIND on the Honeywell TH4210U2002 PRO 4000 5-2 Day Programmable Thermostat means: "Filter" Reminder Displayed. The thermostat is displaying a filter change reminder that was configured in the settings — this is a time-based countdown (not measured by actual filter condition) and means the programmed interval has elapsed; reset the reminder after replacing the HVAC air filter: on most models, go to Preferences or Settings and reset the Filter timer to restart the countdown

How do I fix error code FILTER-REMIND on my Honeywell TH4210U2002 PRO 4000 5-2 Day Programmable Thermostat?

The most successful fix is "Replace HVAC Air Filter and Verify Thermostat Reminder Reset" (medium difficulty, ~30 minutes). Estimated DIY cost: $15-$30. HomeMD has 2 community-ranked fixes for this error.

Is error code FILTER-REMIND on a Honeywell TH4210U2002 PRO 4000 5-2 Day Programmable Thermostat 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 Honeywell TH4210U2002 PRO 4000 5-2 Day Programmable Thermostat error FILTER-REMIND myself?

Yes — the top-ranked community fix ("Replace HVAC Air Filter and Verify Thermostat Reminder Reset") is rated medium difficulty and takes about 30 minutes. Tools needed: None.

How much does it cost to repair Honeywell TH4210U2002 PRO 4000 5-2 Day Programmable Thermostat error FILTER-REMIND?

DIY cost: $15-$30. Professional repair typically costs $100-$180. Many homeowners save money by trying the top-ranked community fix first.

What other error codes does the Honeywell TH4210U2002 PRO 4000 5-2 Day Programmable Thermostat have?

The Honeywell TH4210U2002 PRO 4000 5-2 Day Programmable Thermostat has 8 other known error codes, including: APP-OFFLINE (Thermostat Shows Offline in App), AUX-HEAT ("Aux Heat" Displayed), BLANK-SCREEN (Blank/Dead Display — No Power), BLOWN-FUSE (HVAC Control Board Fuse Blown), COOL-ON-FLASH ("Cool On" Flashing on Display), and 3 more.

Which other Honeywell models have the FILTER-REMIND error?

Error code FILTER-REMIND also appears on 7 other Honeywell models: RTH7600D 7-Day Programmable Thermostat with Backlit Display, RTH9585WF Wi-Fi Color Touchscreen 7-Day Programmable Thermostat, T10 Pro Smart Thermostat with RedLINK Room Sensor, T6 Pro Programmable Thermostat (TH6320WF / TH6220U), T9 Smart Thermostat with Smart Room Sensor, TH6220D1028 FocusPRO 6000 2H/2C Programmable Thermostat, and 1 more. The fix may vary by model, so check each model's specific page for tailored repair steps.

What other error codes does the Honeywell TH4210U2002 PRO 4000 5-2 Day Programmable Thermostat have?

The Honeywell TH4210U2002 PRO 4000 5-2 Day Programmable Thermostat has 8 other known error codes:

APP-OFFLINE — Thermostat Shows Offline in App (2 fixes)
AUX-HEAT — "Aux Heat" Displayed (2 fixes)
BLANK-SCREEN — Blank/Dead Display — No Power (2 fixes)
BLOWN-FUSE — HVAC Control Board Fuse Blown (2 fixes)
COOL-ON-FLASH — "Cool On" Flashing on Display (2 fixes)
EM-HEAT — "Em Heat" or Emergency Heat Mode (2 fixes)
ERR — "Err" Displayed on Screen (2 fixes)
FAN-WONT-STOP — Fan Running Constantly (2 fixes)

Which other Honeywell models have the FILTER-REMIND error?

Error code FILTER-REMIND also appears on 7 other Honeywell models:

RTH7600D 7-Day Programmable Thermostat with Backlit Display (thermostat) · 2 fixes
RTH9585WF Wi-Fi Color Touchscreen 7-Day Programmable Thermostat (thermostat) · 2 fixes
T10 Pro Smart Thermostat with RedLINK Room Sensor (thermostat) · 2 fixes
T6 Pro Programmable Thermostat (TH6320WF / TH6220U) (thermostat) · 2 fixes
T9 Smart Thermostat with Smart Room Sensor (thermostat) · 2 fixes
TH6220D1028 FocusPRO 6000 2H/2C Programmable Thermostat (thermostat) · 2 fixes
TH8321WF1001 VisionPRO 8000 Wi-Fi Programmable Touchscreen Thermostat (thermostat) · 2 fixes

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