Goodman Furnace: Check primary limit control
Check primary limit control on a Goodman furnace: The primary limit is a non-adjustable, automatic reset bi-metal control on the heat exchanger. It should read open only when the heat exchanger is hotter than its setting. Test it cold with the low voltage wires off.
Applies to: Gas furnaces ACVC96/AMVC96/GCVC96/GMVC96 (90% furnaces)
Common causes of check primary limit control
- Limit reads open while cold, meaning it has failed
- Heat exchanger really above the limit setting because of poor airflow
- Wrong limit fitted, with a different temperature setting
- Loose or corroded connection at the limit terminals
How to fix check primary limit control: step by step
- Remove the burner compartment door with power off
- Disconnect the low voltage wires at the limit control terminals
- Use an ohmmeter across the two terminals. It should read continuous unless the heat exchanger is above the limit setting
- If the reading does not match, replace the control
- Use the Primary Limit Charts in the furnace technical manual to confirm part number, temperature setting and color code
- If the limit trips in normal use, check the filter, registers and blower before replacing it
- Reinstall the burner compartment door, restore power, and verify operation
If the unit shows an error code, look it up: Goodman Furnace codes
Source: Goodman GMVC96 service and troubleshooting manual, p. 47-48. 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.