Generac 4700 / QuietPact 40 — Rotor Insulation Test
Testing & diagnosis
For the Generac 4700 / QuietPact 40, from the Generac service manual.
Applies to: Generac 4700, Generac QuietPact 40, Generac GH-220 engine
Before you start
- Do not apply voltage longer than 1 second.
Procedure
- Disconnect wires from the Rotor brushes or remove the brush holder with brushes.
- Connect tester positive (+) lead to positive (+) slip ring (nearest the Rotor bearing).
- Connect tester negative (-) lead to a clean frame ground (such as the Rotor shaft).
- Apply 1000 volts. Do NOT apply voltage longer than 1 second.
- If breakdown is indicated, clean and dry the Rotor and repeat; replace Rotor if it fails the second test.
Tools required
- megohmmeter / hi-pot tester Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 1000 volts applied
- Rotor minimum insulation resistance 1.5 megohms
Full service-parts list: Generac 4700 →, Generac QuietPact 40 →
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.