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The Goodman B1378701 is a genuine OEM 5-pin wiring harness designed as a direct-fit replacement for the GMP075-4 gas furnace. This compact connector harness carries low-voltage signals between the furnace control board and key components such as the ignitor, flame sensor, or pressure switch circuit. Age, heat, and vibration can degrade the original connector, leading to intermittent operation, nuisance lockouts, or a furnace that fails to ignite. Installing a fresh OEM harness eliminates these connection faults and returns the unit to dependable service.
The genuine Goodman OEM harness matches the factory connector keying and pin assignments exactly, so it seats without splicing, crimping, or guesswork. Generic universal harnesses frequently require field modification and can introduce wiring errors that damage the control board. Choosing OEM protects your equipment and preserves warranty coverage.
Easy to Moderate. With power disconnected at the breaker, unplug the old keyed connector and snap the new harness into place. Photograph the routing first to ensure correct orientation. Typical install time is 15–20 minutes for a confident DIYer.
Always shut off electrical power and gas supply before servicing your furnace.