{"product_id":"weil-mclain-591-391-820","title":"Weil McLain 591-391-820 Wiring Harness","description":"\u003cp\u003eThe \u003cstrong\u003eWeil McLain 591-391-820 Wiring Harness\u003c\/strong\u003e is the main \u003cstrong\u003e9-pin control harness\u003c\/strong\u003e on the \u003cstrong\u003eWeil-McLain GV Series 1 and 2\u003c\/strong\u003e gas boiler. The \u003cstrong\u003eWeil-McLain\u003c\/strong\u003e parts list (Fig. 6) describes it as a wiring harness with a \u003cstrong\u003e9 pin connector\u003c\/strong\u003e from the \u003cstrong\u003econtrol module\u003c\/strong\u003e to the \u003cstrong\u003ethermostat\u003c\/strong\u003e, \u003cstrong\u003elimit switch\u003c\/strong\u003e, \u003cstrong\u003epressure switch\u003c\/strong\u003e and \u003cstrong\u003e24VAC gas valve\u003c\/strong\u003e, and notes that it is used with a \u003cstrong\u003eWhite-Rodgers\u003c\/strong\u003e or \u003cstrong\u003eRobertshaw\u003c\/strong\u003e \u003cstrong\u003egas valve\u003c\/strong\u003e and includes the \u003cstrong\u003eblock limit switch\u003c\/strong\u003e. In the photo you can see the \u003cstrong\u003ewhite multi-pin connector\u003c\/strong\u003e at the \u003cstrong\u003econtrol module\u003c\/strong\u003e end, a bundle of colored conductors, insulated \u003cstrong\u003espade terminals\u003c\/strong\u003e, a \u003cstrong\u003ering terminal\u003c\/strong\u003e, and the \u003cstrong\u003esnap-disc limit device\u003c\/strong\u003e riding on the harness with its tag.\u003c\/p\u003e\n\n\u003cp\u003eThis is the harness that ties the safety circuit together. The \u003cstrong\u003ethermostat\u003c\/strong\u003e call, the \u003cstrong\u003elimit switch\u003c\/strong\u003e, the \u003cstrong\u003epressure switch\u003c\/strong\u003e and the \u003cstrong\u003e24VAC gas valve\u003c\/strong\u003e all land on this one assembly and meet at the \u003cstrong\u003econtrol module\u003c\/strong\u003e through a single \u003cstrong\u003emulti-pin plug\u003c\/strong\u003e. That is why a damaged \u003cstrong\u003e591-391-820\u003c\/strong\u003e can look like several different failures: a boiler that will not start on a call for heat, a \u003cstrong\u003epressure switch\u003c\/strong\u003e that never seems to prove, or a \u003cstrong\u003egas valve\u003c\/strong\u003e that never gets power. Because the block limit is part of the harness, a bad block limit is fixed by replacing the harness rather than hunting for a separate limit.\u003c\/p\u003e\n\n\u003cp\u003eBefore you order, compare your harness to the photo. Count the pins in the plug, confirm the same ring and \u003cstrong\u003espade terminal\u003c\/strong\u003e layout, and check that a \u003cstrong\u003esnap-disc limit\u003c\/strong\u003e is built into the harness. Do not confuse it with the \u003cstrong\u003e591-391-819\u003c\/strong\u003e, which is only the lead from the \u003cstrong\u003econtrol module\u003c\/strong\u003e to the \u003cstrong\u003eigniter\u003c\/strong\u003e. When you swap the harness, route it away from the blower housing, the jacket edges and any hot surface, seat every \u003cstrong\u003espade terminal\u003c\/strong\u003e fully, and test the circuit end to end before you leave. Look at the plug housing and the \u003cstrong\u003epressure switch\u003c\/strong\u003e terminals for heat damage while the harness is out, since a burned terminal at either end will take out the new harness too.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eKey Benefits\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n    \u003cli\u003e\n\u003cstrong\u003eOne Harness, Whole Control Circuit:\u003c\/strong\u003e Carries the \u003cstrong\u003ethermostat\u003c\/strong\u003e, \u003cstrong\u003elimit switch\u003c\/strong\u003e, \u003cstrong\u003epressure switch\u003c\/strong\u003e and \u003cstrong\u003e24VAC gas valve\u003c\/strong\u003e circuits to the \u003cstrong\u003econtrol module\u003c\/strong\u003e through one \u003cstrong\u003emulti-pin connector\u003c\/strong\u003e.\u003c\/li\u003e\n    \u003cli\u003e\n\u003cstrong\u003eBlock Limit Switch Included:\u003c\/strong\u003e The \u003cstrong\u003esnap-disc limit\u003c\/strong\u003e is part of the harness, so there is no separate limit to source.\u003c\/li\u003e\n    \u003cli\u003e\n\u003cstrong\u003eListed for GV Series 1 and 2:\u003c\/strong\u003e Shown in the \u003cstrong\u003eWeil-McLain\u003c\/strong\u003e \u003cstrong\u003eGV Series 1 and 2\u003c\/strong\u003e parts list.\u003c\/li\u003e\n    \u003cli\u003e\n\u003cstrong\u003eWorks With Both Gas Valves:\u003c\/strong\u003e \u003cstrong\u003eWeil-McLain\u003c\/strong\u003e notes it is used with a \u003cstrong\u003eWhite-Rodgers\u003c\/strong\u003e or \u003cstrong\u003eRobertshaw\u003c\/strong\u003e \u003cstrong\u003egas valve\u003c\/strong\u003e.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003e\u003cstrong\u003eCommon Questions\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n    \u003cli\u003e\n\u003cstrong\u003eWhat does the 591-391-820 connect to?\u003c\/strong\u003e The \u003cstrong\u003econtrol module\u003c\/strong\u003e to the \u003cstrong\u003ethermostat\u003c\/strong\u003e, \u003cstrong\u003elimit switch\u003c\/strong\u003e, \u003cstrong\u003epressure switch\u003c\/strong\u003e and \u003cstrong\u003e24VAC gas valve\u003c\/strong\u003e, through a \u003cstrong\u003e9-pin\u003c\/strong\u003e connector, per the \u003cstrong\u003eWeil-McLain\u003c\/strong\u003e parts list.\u003c\/li\u003e\n    \u003cli\u003e\n\u003cstrong\u003eDoes it include the block limit switch?\u003c\/strong\u003e Yes. The parts list notes that the harness includes the \u003cstrong\u003eblock limit switch\u003c\/strong\u003e, and the \u003cstrong\u003esnap-disc limit device\u003c\/strong\u003e is visible on the harness in the photo.\u003c\/li\u003e\n    \u003cli\u003e\n\u003cstrong\u003eHow is it different from the 591-391-819 and 591-391-824?\u003c\/strong\u003e The \u003cstrong\u003e591-391-819\u003c\/strong\u003e is only the \u003cstrong\u003econtrol module\u003c\/strong\u003e to \u003cstrong\u003eigniter\u003c\/strong\u003e lead. The \u003cstrong\u003e591-391-824\u003c\/strong\u003e serves the \u003cstrong\u003edual circulators\u003c\/strong\u003e on the \u003cstrong\u003eGV Series 3\u003c\/strong\u003e. The \u003cstrong\u003e591-391-820\u003c\/strong\u003e is the control and safety circuit harness for the \u003cstrong\u003eGV Series 1 and 2\u003c\/strong\u003e.\u003c\/li\u003e\n\u003c\/ul\u003e\n\nDisclaimer: 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.","brand":"Weil McLain","offers":[{"title":"Default Title","offer_id":68025748226226,"sku":"591-391-820","price":108.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1838\/2375\/files\/591-391-820.jpg?v=1794598410","url":"https:\/\/www.gsistore.com\/en-ca\/products\/weil-mclain-591-391-820","provider":"GSIstore","version":"1.0","type":"link"}