Goodman furnace E8: High stage pressure switch closed at the start of the heating cycle
E8 is the high-fire counterpart of E1: the second-stage pressure switch was already closed before the inducer ran, when it should have been open.
Applies to: Goodman GMVC96, GMVM97, GCVC96, GCVM97 and Amana AMVC96, AMVM97 two-stage and modulating gas furnaces with a two-character alphanumeric display. Single-stage furnaces have no high stage switch and cannot produce this code.
What it means
A two-stage furnace carries two pressure switches, one per firing rate, because high fire moves considerably more combustion air and needs its own proof of draft. Both must sit open at rest, and the control checks both before starting. E8 means the high-stage switch was found closed at that check. The reasoning is identical to E1 — a switch stuck closed would prove a draft that does not exist — but the consequence differs slightly in practice: because the fault is in the high-stage circuit, a furnace may still be capable of low-fire operation, so the symptom can be reduced output rather than no heat at all.
Most common causes
- The high stage pressure switch contacts have stuck closed.
- The sensing hose to the high stage switch is pinched or kinked, trapping pressure.
- Water in the high stage sensing hose or its pressure tap.
- A short in the high stage switch wiring.
- The low and high stage switches swapped during a previous repair — a specific and easily missed cause.
- The wrong switch fitted, with a setpoint that does not match the model.
How to diagnose it
- Confirm the furnace is genuinely two-stage or modulating. A single-stage model cannot produce E8.
- Note whether the furnace still produces some heat. Low-fire operation continuing while high fire faults is characteristic.
- Check whether the furnace was recently serviced, since swapped switches are a real cause and a quick check for a technician.
- Check the condensate drain for standing water, which puts moisture where these switches sense.
How to fix it
- Clear a blocked condensate drain if that is present — reasonable homeowner work.
- The pressure switches, hoses, and wiring are technician work, for the same reason as every pressure switch fault: they prove safe venting.
- Ask the technician to confirm the two switches are fitted the right way round if the furnace has been worked on recently.
- Never jumper either switch. Both exist to stop the furnace firing into a flue that cannot carry the products away.
Notes
Because two-stage furnaces can often limp along on low fire, high-stage faults tend to be noticed when the weather turns rather than when they occur. The code is usually present for some time before the house stops keeping up.
Related
All codes for this manufacturer
Goodman and Amana furnace fault codes — every code, with what differs between models.