Goodman furnace d1: Dehumidification, low stage cooling, communicating mode
d1 means the system is removing humidity while cooling on the compressor's low stage, on a communicating system. It is a normal operating mode.
Applies to: Goodman GMVM97, GCVM97 and Amana AMVM97 modulating gas furnaces with a two-character display, on a communicating system with a two stage compressor.
What it means
On a communicating system the furnace, the outdoor unit and the thermostat exchange information rather than simply switching each other on, so the control knows which compressor stage is running and reports it. d1 is dehumidification with the compressor on low stage — the combination that removes the most moisture for the least cooling, because a low stage compressor and a slowed blower together produce a long, gentle, very effective dehumidifying cycle. This is the mode a well set up variable capacity system spends a lot of a humid summer in, and it is the one most likely to be mistaken for underperformance.
Most common causes
- A communicating thermostat calling for dehumidification with the compressor on low stage.
- Humid conditions with a modest cooling load, which is precisely what low stage dehumidification is for.
- A two stage or variable capacity outdoor unit on a communicating system.
How to diagnose it
- Note the weather and the thermostat's humidity setting first.
- Long, low-output cycles are the intended behaviour here rather than a symptom.
- If the house feels cold and clammy rather than cool and dry, the humidity setpoint may be too aggressive.
- Compare against d2, which is the same mode with the compressor on high stage.
How to fix it
- Nothing. This is the system doing its most efficient dehumidification.
- Adjust the humidity setpoint at the thermostat if the system stays in this mode more than wanted.
- Do not interpret the long run times as short cycling or as a fault — they are the opposite.
Notes
Homeowners moving from a single stage system often report that a variable capacity one 'runs all the time'. In this mode that is correct and is why it removes humidity so much better.
Related
- d2 — Dehumidification, high stage cooling, communicating mode
- C1 — Low stage compressor, cooling mode
All codes for this manufacturer
Goodman and Amana furnace fault codes — every code, with what differs between models.
Models this code appears on
From the manufacturer's per-model database. If your model is not listed, this code may not exist on your board, or it may mean something different — check the model page.
What the fix costs
d1 itself has no repair cost — it is the system doing its job. Money enters when the mode gets blamed for a comfort problem: a technician visit to investigate a clammy or cold-feeling house runs a $75–150 diagnostic per the repair cost guide, often credited if work follows. Genuine faults that mimic being stuck in dehumidification live elsewhere — a restricted filter, or on the refrigerant side a low charge, which is outdoor-unit work quoted separately. Before paying for any of it, read the thermostat's humidity setting; a target set unrealistically low for the climate will keep the system in d1 almost permanently at no fault of the equipment.
DIY or call a pro?
The homeowner moves here all happen at the thermostat: raise the humidity setpoint a few points, confirm the mode, change the filter. None of that opens the furnace cabinet. Call a professional when the house stays humid despite long d1 runs — persistent high indoor humidity with the system visibly trying points at charge, airflow, or equipment sizing, all of which need instruments to settle. Do not try to defeat the slowed blower by raising fan speed; the reduced airflow is the mechanism that removes the moisture.
What this looks like
From the outside, this usually shows up as there is no heat but nothing looks obviously wrong — that walkthrough covers what to check in order, and when it stops being a homeowner job.