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1 FLASH

Rheem · Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace

Rheem Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace 1 FLASH Error Fix: Normal — Heat Call Active

The IFC board has received a call for heat from the thermostat and the heating sequence is in progress or has been satisfied. One flash repeated with a pause is the normal operating pattern during a heating cycle. If the furnace shows 1 flash but is not producing heat, verify the gas supply is turned on (the shutoff handle should be parallel to the gas pipe), check that the thermostat is set to HEAT, and confirm the set temperature is above room temperature.

info2 fixes available✨ Free fix available

Quick Answer

Error 1 FLASH on the Rheem Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace means: Normal — Heat Call Active. The top-ranked community fix is “Inspect and Test Furnace Ignition System and Gas Valve” (medium difficulty, ~60 min, DIY cost: $0). 2 community-ranked fixes available below.

Published February 2026 · 2 fixes · furnace

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 furnace 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: $200-$350.

Other Rheem Models with Error 1 FLASH

Rheem R96V 96% AFUE Two-Stage Variable Speed Upflow Gas Furnace

furnace · 2 fixes

Other Rheem Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace Error Codes

10 FLASH

Rollout Switch Open

2 fixes

2 FLASH

System Lockout — Ignition Failed

2 fixes

3 FLASH

Pressure Switch Stuck Closed

2 fixes

4 FLASH

Pressure Switch Stuck Open

2 fixes

5 FLASH

Flame Sensed Without Gas Valve Command

2 fixes

6 FLASH

Power Reversed or No Ground

Low Flame Signal

Igniter Circuit Failure

2 fixes

People Also Ask About Rheem Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace Error 1 FLASH

What does error code 1 FLASH mean on a Rheem Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace?

Error code 1 FLASH on the Rheem Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace means: Normal — Heat Call Active. The IFC board has received a call for heat from the thermostat and the heating sequence is in progress or has been satisfied. One flash repeated with a pause is the normal operating pattern during a heating cycle. If the furnace shows 1 flash but is not producing heat, verify the gas supply is turned on (the shutoff handle should be parallel to the gas pipe), check that the thermostat is set to HEAT, and confirm the set temperature is above room temperature.

How do I fix error code 1 FLASH on my Rheem Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace?

The most successful fix is "Inspect and Test Furnace Ignition System and Gas Valve" (medium difficulty, ~60 minutes). This fix costs nothing. HomeMD has 2 community-ranked fixes for this error.

Is error code 1 FLASH on a Rheem Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace serious?

This error is rated info severity. It is generally not urgent and can often be resolved with a simple DIY fix.

Can I fix Rheem Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace error 1 FLASH myself?

Yes — the top-ranked community fix ("Inspect and Test Furnace Ignition System and Gas Valve") is rated medium difficulty and takes about 60 minutes. Tools needed: Multimeter, Phillips screwdriver, Nut driver set.

How much does it cost to repair Rheem Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace error 1 FLASH?

DIY cost: $0. Professional repair typically costs $200-$350. Many homeowners save money by trying the top-ranked community fix first.

What other error codes does the Rheem Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace have?

The Rheem Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace has 8 other known error codes, including: 10 FLASH (Rollout Switch Open), 2 FLASH (System Lockout — Ignition Failed), 3 FLASH (Pressure Switch Stuck Closed), 4 FLASH (Pressure Switch Stuck Open), 5 FLASH (Flame Sensed Without Gas Valve Command), and 3 more.

Which other Rheem models have the 1 FLASH error?

Error code 1 FLASH also appears on 1 other Rheem model: Rheem R96V 96% AFUE Two-Stage Variable Speed Upflow Gas Furnace. The fix may vary by model, so check each model's specific page for tailored repair steps.

What other error codes does the Rheem Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace have?

The Rheem Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace has 8 other known error codes:

10 FLASH — Rollout Switch Open (2 fixes)
2 FLASH — System Lockout — Ignition Failed (2 fixes)
3 FLASH — Pressure Switch Stuck Closed (2 fixes)
4 FLASH — Pressure Switch Stuck Open (2 fixes)
5 FLASH — Flame Sensed Without Gas Valve Command (2 fixes)
6 FLASH — Power Reversed or No Ground (2 fixes)
7 FLASH — Low Flame Signal (2 fixes)
8 FLASH — Igniter Circuit Failure (2 fixes)

Which other Rheem models have the 1 FLASH error?

Error code 1 FLASH also appears on 1 other Rheem model:

Rheem R96V 96% AFUE Two-Stage Variable Speed Upflow Gas Furnace (furnace) · 2 fixes

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