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American Standard E04: Open limit

Source: American Standard manual (PDF) (opens in a new tab) ↗ · Updated

Status codeE04American Standard
What does American Standard E04 mean?

Open limit: the main thermal limit, a rollout switch, or the reverse airflow switch.

Call a pro: jump to when to call a pro Equipment type: furnace
How it shows: 7-segment display on an American Standard S9V2 two-stage variable-speed furnace: E04

American Standard S9V2 E04 is an open limit. The guide names three switches: the main thermal limit, a rollout switch, or the reverse airflow switch. It does not add a filter sentence on this row. The sequence proves all three closed before the inducer starts. If the burners show scorching, treat it as rollout: furnace off, and a technician finds the cause before any manual reset.

Likely causes

  • Main thermal limit open
  • Rollout switch open
  • Reverse airflow switch open

Safe checks for E04

  1. If you see scorching at the burners, or you smell hot metal or combustion odor, turn the furnace off and leave it off
  2. The heating sequence proves the rollout switches, the main thermal limit and any reverse-airflow switch closed before the inducer starts
  3. Technicianfind which of those switches is open before any manual reset
Safety firstIf you smell gas, do not touch any electrical switch or use a phone in the building; leave immediately and call your gas supplier from outside. Turn off electrical power at the furnace switch or breaker before opening any panel, and never bypass or jumper a limit, rollout or pressure switch. Gas valve, burner, venting, wiring and control-board work should be done by a licensed HVAC technician.

Capacitors can hold a charge after the power is off. Safety terms.

When to call a pro

Call a licensed HVAC technician. E04 names three different safety switches. Do not jumper a limit or reset a rollout switch to finish the night.

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Parts & tools for this fix

Taken from this code's causes or steps. A search link opens Amazon results and does not confirm a fit. Check the model number in the manual.

Furnace pressure switch hose: guide

Technician step in this code: find which of those switches is open before any manual reset

See the guide for what to look for when buying one.

Furnace inducer (draft) motor: guide

In this code: The heating sequence proves the rollout switches, the main thermal limit and any reverse-airflow switch closed before the inducer starts

This one is for a technician to test or replace, so we only explain it and do not link to buy it.

High limit and rollout switches: guide

In this code: Main thermal limit open

A safety device: we explain it but do not link to buy one.

Related American Standard codes

E05Flame was detected when it shouldE09Open inducer limit switch, or openE12Open fuseE08Flame current is low, but stillE2.1Retry exceededE2.2Recycles exceeded

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