Generac — Testing the Weekly Exercise Circuit
Testing & diagnosis · Weekly exercise circuit / SW1
From a Generac service manual covering: 4077, 4079, 4109, 4389, 4390, 4456, 4674, 4675. Check it applies to your exact model before use.
Applies to: Generac 4077, Generac 4079, Generac 4109, Generac 4389, Generac 4456
Before you start
- Be careful when pushing the SW1 switch, there is LIVE voltage present on the PCB.
Procedure
- Remove the DC fuse from the control panel.
- Open the control panel front (be careful not to short any wiring).
- Remove the cover from the CMA box.
- Locate SW1 on the circuit board (76009-A) in the upper right corner.
- Install the fuse back in the control panel.
- Put the Auto-Off-Manual switch in the Auto position.
- Push and hold SW1 with a non-conductive device until the unit starts (about 30 seconds); the unit will run about 20 minutes then shutdown.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Full service-parts list: Generac 4077 →, Generac 4079 →, Generac 4109 →, Generac 4389 →, Generac 4456 →
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.