Generac — CTTS 600-2600 Amp: Switch Will Not Transfer to Standby
Testing & diagnosis · Contactor Assembly (CTTS 600-2600 Amp)
From a Generac service manual — check it applies to your exact model before use.
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Before you start
- Disable generator from starting; disconnect negative battery cable.
Procedure
- Remove cover. Refer to Figure 1 for PCB layout.
- For testing, follow PCB numbering in Figure 2.
- Measure resistance on Trip Coil between J1-1 and J1-3 on PCB1. Refer to chart. If not proper, replace Trip Coil.
- Test ATS limit switch. Measure resistance between AT1 and J2-1 (PCB1): less than 4 ohms. Measure resistance between AT2 and J2-2 (PCB1): less than 4 ohms. If INFINITY, replace ATS limit switch (071345
- If steps 3 and 4 good and switch not tripping to neutral, replace PCB 1 (082428).
- If switch tripping to neutral but will not close to standby, and standby voltage at B1(107B) and B2(205), measure resistance between PCB2 J1-7 and J1-8. Closing coil resistance should be measured.
- Test BX limit switch. Measure resistance between B1 and PCB2 J2-6. Measure resistance between B2 and PCB2 J2-5. Less than 4 ohms. If INFINITY, replace BX limit switch (071345).
- If closing coil and BX limit switch test good, replace PCB 2 (082428).
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- less than 4 ohms
- INFINITY
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.