Goodman Furnace: Alternate combustion air opening (upflow or horizontal)
Alternate combustion air opening (upflow or horizontal) on a Goodman furnace: When the alternate vent location is used (horizontal left side down, or downvent vertical), an alternate combustion air opening can be used. The locating dimple is on the right side of the cabinet, 1 7/8 in. from the front edge, in line with the knockout. The idea is to move the air inlet to match the new vent position so the piping lines up.
Applies to: Upflow and horizontal models using alternate venting
Common causes of alternate combustion air opening (upflow or horizontal)
- Horizontal left side down installation
- Downvent vertical installation
- Standard air opening conflicting with the pipe route
- Tight space needing the inlet moved
How to fix alternate combustion air opening (upflow or horizontal): step by step
- Remove the screws and combustion air flange from the cabinet.
- Insert the cabinet plug in the unused combustion air hole so it is sealed.
- Drill a pilot hole at the cabinet dimple, sized for the knockout tool.
- Use a knockout tool to make a 3 in. diameter hole, then deburr the edge.
- Install the combustion air flange and secure it with the screws from the first step.
- Reinstall the flange screws to secure the flange to the cabinet.
- Check that the flange is sealed with no air leaks.
If the unit shows an error code, look it up: Goodman Furnace codes
Source: Goodman GMVC96 service and troubleshooting manual, p. 15. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.