Generac 91401256S / Bsc 556 — Testing Rotor Insulation on Direct Excited Units
Testing & diagnosis · rotor assembly
For the Generac 91401256S / Bsc 556, from the Generac service manual.
Browse Generac generators & specs →
Procedure
- Gain access to rotor brushes and slip rings.
- Disconnect all wires from brushes or remove brush holders.
- Connect red hi-pot tester probe to positive slip ring nearest rotor bearing.
- Connect black tester probe to clean frame ground.
- Turn hi-pot tester switch off, plug into 120 VAC outlet.
- Set voltage selector to 500 volts, turn tester on and check pilot lamp.
- Set voltage selector to 1250 volts and observe breakdown lamp, then turn tester off.
- If breakdown lamp comes on, drying may be necessary; after cleaning and drying repeat test.
- If rotor fails second test, replace it.
Tools required
- hi-pot tester Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 500 volts
- 1250 volts
- one second maximum
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.