Generac — Testing the Battery Charger
Testing & diagnosis · Battery charger circuit
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
- If the battery voltage measures greater than 13 volts it should be discharged to less than 12.6 volts.
Procedure
- Set the exercise timer per the Owner's Manual (this sets the PCB to the zero reading).
- Remove the DC fuse from the control panel.
- Measure the DC voltage at the battery (+)(-) and record; if greater than 13 volts discharge it to less than 12.6 volts.
- Measure current across the fuse holder with the fuse removed (current flow should be into the battery, typically in the .5 amp range).
- If current cannot be measured, reinstall the fuse and measure battery voltage; over ten to fifteen minutes a slow increase should be seen.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- .5 amp range typical charge current
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.