York Furnace Error Code E5 — What It Means
York furnace error code E5 indicates a high-limit switch trip — the furnace’s primary safety control detected that the heat exchanger temperature exceeded the safe operating limit and opened the circuit to shut down the gas valve. On York furnaces, the high-limit switch is a normally-closed temperature-sensitive switch mounted on or near the heat exchanger. When it reaches its trip temperature (typically 150–190°F depending on the model), it opens and the furnace shuts off.
E5 appears on York TM9V, TG9S, YP9C, YG9S, and compatible Johnson Controls OEM furnaces (Luxaire, Heil, Tempstar share the same codes).
Causes of York E5 Error
| Cause | Likelihood | First Check |
|---|---|---|
| Dirty / clogged air filter | Very High | Replace filter immediately |
| Closed or blocked supply registers | High | Open all registers; remove obstructions |
| Dirty evaporator coil (if AC installed) | High | Check coil for dirt buildup |
| Undersized return air | Medium | Check return air grille size vs. system |
| Failing blower motor | Medium | Verify blower runs at full speed |
| Cracked heat exchanger (recirculation) | Lower | Look for soot around heat exchanger seams |
| Failed high-limit switch (opens prematurely) | Lower | Test switch continuity at room temperature |
Step-by-Step Diagnosis
Step 1: Replace the air filter A clogged air filter is by far the most common cause of E5 on York furnaces. Even a filter that looks moderately dirty can restrict airflow enough to cause limit trips in cold weather when heating demand is highest. Replace the filter with a new one rated at the same MERV level or lower (high-MERV filters restrict airflow more than standard filters).
Step 2: Check and open all registers Walk through the building and verify every supply and return register is fully open. Closed registers force the furnace to push more air through fewer openings, increasing static pressure and reducing airflow across the heat exchanger.
Step 3: Check blower operation After replacing the filter, run the system and verify the blower starts within 30–60 seconds of the burners igniting. The blower wheel should be clean — a dirt-caked wheel can lose 20–30% of its airflow capacity. Inspect the blower wheel and clean it if needed.
Step 4: Verify limit switch position After allowing the furnace to cool, use a multimeter to test the high-limit switch contacts for continuity. At room temperature, a good switch should show continuity (closed). If the switch shows open at room temperature, the switch has failed in the open position and must be replaced — this is uncommon but does occur on older furnaces.
Step 5: Inspect for cracked heat exchanger If E5 occurs repeatedly with no obvious airflow restriction, inspect the heat exchanger for cracks. Signs of a cracked heat exchanger: soot deposits on the outside of the exchanger, CO levels in the conditioned air, or flame disturbance visible through the sight glass when the blower starts. A cracked heat exchanger is a safety emergency — call a technician.
Resetting After E5
After fixing the root cause, the high-limit switch typically auto-resets once the heat exchanger cools below the reset temperature (usually 30–50°F below the trip temperature). This takes 5–15 minutes. If the limit does not auto-reset after 20 minutes, it may have failed in the open position and needs replacement.
When to Call a Pro
Any suspicion of a cracked heat exchanger requires immediate professional inspection. Carbon monoxide can enter the conditioned airspace through a cracked heat exchanger — install a CO detector near the furnace if you don’t already have one.