Weil McLain 591-391-819 Wiring Harness
The Weil McLain 591-391-819 Control Module to Igniter Wiring Harness is the short OEM wiring harness that carries power from the control module to the hot surface igniter on a Weil-McLain GV gas boiler. Weil-McLain lists it in the ignition controls group of the GV Series 1 and 2 parts list (Fig. 4) as a wiring harness from the control module to the igniter, and in the GV Series 3 parts list (Fig. 6) as "Wiring Harness, Control Module to Hot Surface Igniter." The harness is a two-wire lead with black and white conductors, a red two-position connector on one end and a white mating connector on the other, so it plugs in at both ends with no splicing and no crimping. The wire is printed with its gauge and temperature rating along the jacket.
On a hot surface ignition boiler the control module decides when the igniter gets power, and this harness is the only path between the two. The igniter itself is a separate part. The GV parts lists show the 511-330-148 igniter replacement kit, which includes a Norton 271Y igniter, a gasket and screws, and the 590-317-599 igniter gasket is listed beside it. Keep these three numbers straight when you diagnose a boiler that is not lighting: 511-330-148 is the igniter, 590-317-599 is the gasket that seals it, and 591-391-819 is the harness that feeds it.
When a GV boiler locks out without the igniter ever glowing, the harness belongs on your checklist before you condemn the igniter or the control module. Look at both connector housings for discoloration, melting or a terminal that has backed out of its cavity, because a loose pin runs hot and gets worse with every call for heat. Check the insulation where the harness passes the blower housing and the jacket edges for chafing, then disconnect both ends and test each conductor for continuity. A harness with a cooked connector should be replaced rather than cleaned, since the damage is inside the housing where you cannot reach it. Route the new harness the way the old one ran, away from hot surfaces and sharp edges, and seat both connectors until they latch.
Key Benefits
- Dedicated Ignition Path: Connects the control module to the hot surface igniter and does nothing else, which keeps diagnosis simple.
- Listed by Weil-McLain: Shown on the GV Series 1 and 2 parts list and on the GV Series 3 parts list.
- Plug-In Connectors: A red two-position connector and a white mating connector are already on the leads, so there is no splicing or crimping.
- Pairs With the Igniter Parts: Order alongside the 511-330-148 igniter kit and the 590-317-599 gasket when the whole ignition circuit is being refreshed.
Common Questions
- What does the 591-391-819 connect? It connects the control module to the hot surface igniter on the GV boiler, as the Weil-McLain parts lists describe it.
- Is this the same as the other GV harnesses? No. The 591-391-820 is the 9-pin control harness for the thermostat, limit, pressure switch and gas valve, and the 591-391-824 serves the dual circulators on the GV Series 3. The 591-391-819 is the igniter lead.
- How do I tell a bad harness from a bad igniter? Check the connector housings and the continuity of each conductor with the harness unplugged at both ends. If the harness tests good and the igniter does not glow, move on to the igniter and the control module.