Lennox E250 — Limit switch circuit open

What this error means

The high-temperature limit opened — the furnace overheated, and if the limit doesn't reclose within 3 minutes the control takes a 1-hour soft lockout. Same story as every brand's limit code: it's almost always airflow (dirty filter, blocked returns, dirty coil or blower).

Symptoms

• Short-cycling heat
• E250 displayed
• Weak airflow at registers

Try this first (safe DIY steps)

1. Fresh, correct-spec filter; open registers; clear returns
2. Power off 30 seconds and restore (or wait out the 1-hour lockout)
3. If it recurs with good airflow, stop resetting

Safety: power off before any physical intervention. Never bypass covers or interlocks — fuser areas run hot enough to burn.

When to call a technician

Persistent E250 despite airflow fixes = blower/coil service or limit switch replacement ($150–$400).