Marathon — Generator Drying - Short-Circuit Method
Maintenance · Generator winding
From a Marathon service manual — check it applies to your exact model before use.
Before you start
- Do not exceed nameplate amps.
Procedure
- Disconnect exciter leads F1 and F2 from the regulator.
- Connect a battery or dc power source of approximately 12-24 volts to exciter leads F1 and F2.
- Short circuit the generator lead wires to each other (L1 to L2 to L3).
- Start the generator set and measure current through the leads with a clip-on ammeter.
- Adjust voltage source to approximately 80% of rated ac nameplate current, never exceeding nameplate amps.
- Run and check insulation resistance every one to four hours until a fairly constant value of 1.5 megohms or greater is obtained.
- Disconnect dc power source and reconnect F1 to F+ and F2 to F-.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 80% rated ac nameplate current
- 1.5 megohms or greater
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.