Low flame signal / faulty flame sensor: the sensor is dirty or failing
The 7-FLASH error code on Goodman boilers indicates low flame signal / faulty flame sensor: the sensor is dirty or failing.
Goodman 7-FLASH means: low flame signal / faulty flame sensor: the sensor is dirty or failing. The usual causes are thermistor (ntc sensor) failure — open circuit or short circuit, loose or corroded wiring connection at the sensor or sensor out of calibration giving incorrect readings. A Gas Safe registered engineer should diagnose the root cause.
What Does 7-FLASH Mean
The 7-FLASH code is shown by the boiler’s control board when it detects low flame signal / faulty flame sensor: the sensor is dirty or failing. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| The display shows 7-FLASH and the boiler stops until the fault is cleared |
Common Causes
Causes documented in 2 technical sources.
| Cause |
|---|
| Thermistor (NTC sensor) failure — open circuit or short circuit |
| loose or corroded wiring connection at the sensor |
| sensor out of calibration giving incorrect readings |
| water damage to the sensor or its wiring |
| PCB input fault — the connector on the PCB may be damaged |
Safety Warning
7-FLASH is a gas-related fault. Never attempt to repair or adjust the gas valve, burner assembly, or flue system yourself. All gas work must be carried out by a Gas Safe registered engineer (UK) or licensed HVAC technician (US). Repeated resets after ignition failure can cause unburnt gas to accumulate inside the combustion chamber — this is a serious safety hazard. If you smell gas at any point, turn off the gas supply at the meter, open windows, leave the property, and call your gas emergency service immediately. Gas-related fault. Do not open the furnace cabinet or work on the gas valve, burner, igniter or venting yourself. Repeated resets are unsafe. Have it diagnosed and repaired by a licensed HVAC technician.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
Identify which sensor is faulty from the error code (flow, return, DHW, flue gas, or outdoor)
Check the wiring — inspect the connections at both the sensor and the PCB for corrosion or loose terminals
Measure the sensor resistance with a multimeter — compare with the manufacturer's resistance/temperature chart (typically 10kΩ at 25°C (77 °F) for NTC sensors)
If resistance is out of range (infinite = open circuit, near zero = short circuit), replace the sensor
If resistance is correct, check the wiring continuity between the sensor and PCB
If wiring is good, test the PCB input
How to Fix It
Replace the faulty thermistor/NTC sensor
repair or replace damaged wiring
clean corroded connectors
if the PCB input is damaged, replace the PCB
Refer to the Goodman service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
Diagnostic Tools
TroubleAtlas Score
What Is the TroubleAtlas Score?
Every boiler model is independently evaluated and scored by TroubleAtlas across 6 dimensions: reliability, efficiency, parts availability, service network, value for money, and user satisfaction. The score helps you compare models and make informed decisions when choosing a new boiler.
See All Boiler Scores →Boiler Breakdown Cover
Boiler Breakdown Cover
Protect against unexpected repair costs. Cover plans include annual service, emergency callouts within 24 hours, and full parts replacement. Compare plans side by side and choose the level of protection that fits your home and budget.
Coverage Plans — Coming SoonConsidering a New Heating System
Considering a New Heating System?
If your boiler or heat pump is over 10 years old, replacing it with a modern condensing boiler or air-source heat pump could save you up to 30% on energy bills and significantly reduce your carbon footprint.
Compare Heating System Prices →
YouTube Channel
Watch the fixes. Follow the channel.
Step-by-step boiler repair guides, equipment reviews, and heating system comparisons from qualified engineers.
New fixes every weekFix in 5
Quick fixes for common boiler faults explained in under 5 minutes
Boiler Comparator
Side-by-side comparisons of popular boiler models
Boiler Reviews
Independent reviews with TroubleAtlas Score ratings
Find a Specialist
Don’t fix it alone. Find a trusted heating engineer near you.
TroubleAtlas connects you with vetted local heating professionals who can inspect, diagnose and repair your boiler safely — no guesswork, no unnecessary call-outs.
Local heating professionals are coming to your area
We’re onboarding Gas Safe registered and licensed HVAC engineers city by city. Check back soon, or search above to see current availability.
TroubleAtlas Pro
Get cited by AI. Get found by customers.
TroubleAtlas Pro puts your business in front of homeowners searching for exactly this fault, and structures your listing so AI assistants can cite you as a trusted source.
- ✓ Appear on error code pages viewed by thousands of homeowners
- ✓ AI assistants cite your listing as a verified local specialist
- ✓ Receive direct leads with customer name and contact details
- ✓ TroubleAtlas Certified badge for your marketing materials
Affected Models
Goodman models that can display fault code 7-FLASH:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Goodman models | — | Possible |
Frequently Asked Questions
Replace the faulty thermistor/NTC sensor. According to the technical documentation, this is the first check on the list for 7-FLASH.
7-FLASH is classified as a high-severity fault: it involves gas, combustion or flue components. Do not keep resetting the boiler and do not attempt the repair yourself — call a Gas Safe registered engineer.