Generac — Wn 100-400 Amp: Switch Will Not Retransfer to Utility

Testing & diagnosis · Contactor Assembly (Wn 100-400 Amp)

From a Generac service manual — check it applies to your exact model before use.

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Procedure

1. Remove front cover.
2. For testing, note PCB layout (see Figure 2).
3. If switch not tripping to neutral, measure resistance between J2-6 and J2-7. Trip coil resistance should be measured. If INFINITY, replace trip coil.
4. Remove single Phillips head screw holding PCB. Unplug male to female connector. Verify contactor in utility position. On female side, measure ohms between Blue and Gray wires: 0.2 ohms. Measure ohms b
5. If steps 3 & 4 good, switch should be tripping to neutral.
6. If not in neutral, push manual trip button to trip to neutral.
7. Measure resistance between A1 and J3-2. 0.2 ohms. If INFINITY, verify neutral position and test AXBX limit switch. If AXBX good, test select LS: place meter lead on upper front contact of AXBX and oth
8. Measure resistance between A2 (J1-2) and J3-1. 0.2 ohms. Push down select coil button: open or INFINITY. If INFINITY, verify neutral and measure ohms between J1-2 and J3-4: 0.1 ohms. If open or INFINI
9. If 0.1 ohms between J1-2 and J3-4, measure resistance between J3-4 and J3-1: 0.2 ohms. If open or INFINITY, replace select LS (074672A).
10. If all tests satisfactory, replace PCB.

Source: Generac service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.

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