Goodman furnace E1: Low stage pressure switch closed at the start of the heating cycle

E1 means the control checked the low stage pressure switch before starting the inducer and found it already closed. It is supposed to be open at rest, so the sequence stops there.

Applies to: Goodman GMVC96, GMVM97, GCVC96, GCVM97 and Amana AMVC96, AMVM97 series gas furnaces with a two-character alphanumeric display.

What it means

The pressure switch proves the draft inducer is genuinely moving air before any gas is released, and it does that by sensing suction. At rest, with the inducer off, it must sit open. The control verifies that at the start of every cycle, because a switch stuck closed would prove a draft that does not exist — and a furnace that fires believing it has draft when it has none can push combustion products into the house. Finding the switch closed before the inducer has run, the control refuses to continue. This is the interlock working as designed, and the code is telling you something specific rather than pointing at a general area.

Most common causes

• The pressure switch contacts have welded or stuck closed and no longer open when the inducer stops.
• The sensing hose is pinched or kinked in a way that traps pressure.
• Water in the sensing hose or the pressure tap, holding the switch closed.
• A short in the switch wiring, which is electrically indistinguishable from closed contacts.
• The wrong pressure switch fitted at a previous repair — these are rated per model and are not interchangeable.
• The low and high stage switches swapped during service.

How to diagnose it

1. Note whether the inducer motor starts at all. On this fault it usually does not, because the control stops before that step.
2. Check whether the furnace was serviced recently. A hose or switch disturbed during other work is a common trigger for this appearing suddenly.
3. Look for condensate problems — a drain that has been backing up puts water where this switch senses.
4. Check the display for a stored code as well as the active one; E1 and E2 are opposite halves of the same test and both may have occurred.

How to fix it

1. Clearing a blocked condensate drain is a reasonable homeowner task and is worth doing, since it causes several related faults.
2. The pressure switch, its hoses, and its wiring are technician work. The switch proves safe venting, and a furnace running with it defeated can vent combustion products, including carbon monoxide, indoors.
3. Never jumper a pressure switch to get heat. It is the only thing between a blocked flue and a firing burner.
4. Replace a failed switch with the exact part for the model. The setpoint is model-specific and a near-match is not a match.

Notes

E1 and E2 are the two failure directions of one test — one says the switch is closed when it should be open, the other says it will not close when it should. Reading the wrong one sends the diagnosis in completely the wrong direction.

Related

• E2 — Low stage pressure switch stuck open
• E8 — High stage pressure switch closed at cycle start

All codes for this manufacturer

Goodman and Amana furnace fault codes — every code, with what differs between models.

Sources

• Goodman Manufacturing — Diagnostic Code Identification System (model-specific fault code lookup)