Weil McLain 591-391-824 Wiring Harness
The Weil McLain 591-391-824 Dual Circulator Wiring Harness connects the control module to the system circulator and the by-pass circulator on the Weil-McLain GV Series 3 gas boiler. The GV Series 3 parts list shows it twice: in the ignition controls group (Fig. 7) as "Wiring Harness, Control Module to System and By-Pass Circulators," and again in the trim group (Fig. 8) as "Wiring Harness, Dual Circulators to Control Module." The photo shows a black jacketed cable with two strain-relief fittings at the circulator ends, green and white conductors, and a white plug connector for the control module end.
A dual circulator harness matters because the GV Series 3 control module runs two pumps: the system circulator that moves water through the heating loop and the by-pass circulator that works with the boiler loop. Both pumps are powered from the control module, and this single harness carries that power. When one pump does not run, or both quit together, the harness is a common culprit, especially at the strain-relief fittings where the jacket is squeezed and at the plug where terminals can back out.
To check it, shut off power and look at the strain-relief fitting at each circulator end for a cracked jacket or exposed conductor, then look at the white plug for browning or a loose pin. Test each conductor for continuity from the plug to the circulator end before you condemn a pump or the control module. Order by the number on the harness and match the photo: a black cable with two strain-relief fittings and a single white plug. Related GV harnesses are the 591-391-819, which feeds the igniter, and the 591-391-820, the 9-pin control circuit harness used on the GV Series 1 and 2.
Key Benefits
- Powers Both Circulators: One cable runs the system circulator and the by-pass circulator from the control module.
- Listed for GV Series 3: Shown twice on the Weil-McLain GV Series 3 parts list, in the ignition controls and trim groups.
- Strain-Relief Fittings Included: The two strain-relief fittings at the circulator ends are already on the cable.
- Plug-In Control End: A white plug connector seats at the control module, so there is no splicing.
Common Questions
- What does the 591-391-824 connect? The control module to the system and by-pass circulators on the GV Series 3 boiler, per the Weil-McLain parts list.
- Is it for a single circulator? No. The parts list calls it the dual circulator harness, and the photo shows two circulator-end fittings.
- What should I check before replacing it? Check the strain-relief fittings, the jacket, the white plug and the continuity of each conductor. If both circulators run when powered directly, the harness is the likely fault.