Check wiring

What is going on

A visual and continuity check of the wiring on the GMVC96 family furnace. Do it with the power off and confirmed dead, since the wiring carries line voltage. Burnt or loose connections are a common hidden cause of intermittent faults, so look carefully before replacing parts.

Likely causes

• Overheated or damaged wire insulation
• Loose or corroded connections
• A broken conductor that reads open on the meter

Check in this order

1. Shut off power at the disconnect and verify with a meter that it is dead.
2. Look for signs of overheating, damaged insulation and loose connections.
3. Use an ohmmeter to check continuity of any wire you suspect is open.
4. If a wire must be replaced, use AWM 105°C wire with 2/64 inch insulation of the same gauge or equivalent.
5. Re-secure the wiring away from sharp edges and hot surfaces.
6. Restore power and confirm the furnace runs a full cycle.

More furnace guides

• Airflow lower than demanded, furnace runs on low stage when high stage is expected
• Alternate combustion air opening (upflow or horizontal)
• Alternate vent/flue location (upflow or horizontal left)
• Annual inspection checklist
• Auxiliary limit control (location and purpose)
• Auxiliary limit switch open (blower compartment)