Weil McLain 591-391-821 Wiring Harness

The Weil McLain 591-391-821 Wiring Harness with Junction Box is a factory wiring harness that includes its own junction box. The part number appears in Weil McLain's GV Series 1 and 2 parts list and again in the GV Series 3 parts list, which makes it a manufacturer-listed component for those gas boiler families. It is not a universal harness, and it is not listed for every GV model, so the part number should be matched against the boiler's own parts list.

A junction box on a boiler harness gives the wiring a defined connection point, so field connections are made in an enclosure rather than in the open. When that box is cracked, the harness insulation is brittle from years of heat, or terminals inside are corroded, the whole assembly is better replaced as a unit. Using the factory 591-391-821 keeps the wire gauges, lengths and terminations the way the manufacturer built them and avoids the problems that come from patching a harness with mismatched wire or loose connectors.

Check the old harness and junction box against the part number before you order. Weil McLain uses different harness numbers on other boiler lines, including the GV90+ family, so a GV Series 1, 2 or 3 boiler is the match for this one. If you are not sure which series you have, send the boiler model and serial number and our team will help confirm the right harness before you buy.

Key Benefits

• Listed for GV Series 1, 2 and 3: 591-391-821 appears in the Weil McLain GV Series 1 and 2 parts list and in the GV Series 3 parts list.
• Harness and Junction Box Together: The harness comes with its junction box, so the wiring connection point is replaced along with the wire.
• Factory Wire and Terminations: Built to the manufacturer's layout, which avoids the mismatched wire and loose connectors that field repairs invite.
• One Part Number to Match: 591-391-821 is the number to check against the old harness or the boiler parts list.

Common Questions

• What is the 591-391-821? It is a Weil McLain wiring harness with a junction box, listed in the GV Series 1 and 2 parts list and in the GV Series 3 parts list.
• Will it fit a GV90+ boiler? We do not list it for the GV90+. That family uses different harness numbers, so please send your boiler model and serial number and our team will confirm.
• Should I replace the junction box with the harness? Yes, when the harness and box are supplied together. A cracked box or brittle insulation is the usual reason to replace the whole assembly.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.