Error Code 4 FLASHES

Goodman GMSS960803BN Error Code 4 FLASHES: Open limit switch

TL;DR

Open limit switch

Disclaimer

This article is for informational purposes only and does not guarantee the accuracy or completeness of the information provided. Always turn off power and gas supply before attempting any repairs. If you smell gas, leave immediately and call your gas company. Consult a licensed HVAC technician for diagnosis and repair. Any actions taken based on this information are at your own risk.

What Does Code 4 FLASHES Mean?

Open limit switch

Common Causes

Cause	Likelihood	DIY?
Faulty primary or auxiliary limit switch	Most common	✗ Call a pro →
Dirty or blocked air filter	Common	✓ DIY fix →
Restrictive ductwork	Common	✗ Call a pro →
Improper circulator blower speed	Uncommon	✗ Call a pro →
Failed circulator blower	Uncommon	✗ Call a pro →

When to Call a Professional

Contact a licensed HVAC technician if:

Basic troubleshooting did not resolve the error
You smell gas at any point during the process
You are not comfortable working around gas lines or electrical components
The unit needs a gas valve, control board, or motor replacement

Sources

Goodman GMSS96 Installation Instructions Manual