Marathon — Insulation Resistance Inspection
Maintenance · generator stator
From a Marathon service manual — check it applies to your exact model before use.
Before you start
- Do not use a megger on the rotor without disconnecting the diode bridge.
- Do not use a megger on the exciter field without first disconnecting the field leads from the regulator.
Procedure
- Connect all stator leads together.
- Measure insulation resistance from lead terminals to stator frame with a megohmmeter.
- A reading of at least 0.5 megohm (500,000 ohms) indicates insulation is in good condition.
- Record readings for comparison with future data.
Tools required
- megohmmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 0.5 megohm minimum
Source: Marathon 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.