Generac — Wn 100-400 Amp: Switch Will Not Transfer to Generator

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, +/- 7%. 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 yellow and brown wires: 0.2 ohms. Measure ohm
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. Measure ohms between J2-4 and J2-5. Select coil resistance should be measured. If INFINITY, replace select coil.
7. Measure resistance between B2 and J3-3. 0.2 ohms. If INFINITY, replace PCB or check solder points/trace on back of PCB.
8. Measure resistance between B1 and J2-4. 1.6 M ohms. If INFINITY, test AXBX limit switch.
9. Measure ohms between back contacts on AXBX limit switch (blue wires): 0.2 ohms. If open, replace AXBX limit switch (071345).
10. If steps 6 and 7 good, select coil should be energizing. Test closing coil. Measure resistance between J2-1 and J2-3. Closing coil resistance should be measured.
11. Measure resistance between B1 (J1-3) and J3-2. Open or INFINITY. Push down select coil button: 0.2 ohms. If INFINITY, test AXBX limit switch.
12. Verify switch in neutral. Measure resistance between two front contacts with yellow wires: 0.2 ohms. If open or INFINITY, replace AXBX limit.
13. If AXBX good, replace select LS (074672A).
14. Measure resistance between B2 and J3-1. INFINITY. Push down select coil button: 0.2 ohms. If INFINITY, replace LS (074672A).
15. 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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