Goodman furnace H: Gas heat demand, followed by the demand percentage

H is not a fault. It introduces the current gas heat demand as a percentage — the firing rate the furnace has chosen for the conditions.

Applies to: Goodman GMVM97 and GCVM97 modulating gas furnaces with a two-character alphanumeric display.

What it means

A modulating furnace does not simply have low and high fire; it varies its output continuously across a range, and H tells you where in that range it currently is. The display shows H followed by the demand percentage. This is the clearest window into how a modulating furnace actually behaves: on a mild day it may sit at 40 per cent for hours, producing steady gentle heat, where a single-stage furnace would cycle on and off at full output. Understanding that is worth something, because a modulating furnace running at low demand for long periods is doing exactly what it was bought to do.

Most common causes

Not applicable — this is an operating data display rather than a fault.

How to diagnose it

Recognise that this is data rather than a fault.
Note the percentage that follows the H, since that is the information.
Note whether the demand varies with the weather, which is the expected behaviour.
A furnace permanently at 100 per cent demand in mild weather is worth asking about, since it suggests modulation is not working as intended.

How to fix it

Nothing to fix. This is the furnace reporting its own firing rate.
If the furnace runs at maximum demand constantly in mild conditions, mention it at the next service — it may indicate a staging or configuration issue.
If the house is not keeping up at high demand, check the air filter and registers first.
Use this reading when discussing performance with a technician rather than describing it in general terms.

Notes

The whole point of a modulating furnace is long, low, steady runs rather than short bursts at full output. Seeing a low demand percentage on a mild day is confirmation the furnace is working as designed, not evidence it is underperforming.

Sources

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

This site is a reference, not a substitute for a licensed HVAC technician. Gas appliances can leak carbon monoxide and cause fire. Anything involving gas lines, the heat exchanger, or the flame sensing circuit should be handled by a licensed professional. Pages are written with AI assistance from the sources listed on each page and checked against them before publishing.