Cummins/Onan — Dynamic Rotor/Stator Test [D]
Testing & diagnosis · Voltage regulator / generator
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan HDKA, Cummins/Onan HDKAQ, Cummins/Onan HDKAR
Before you start
- Electrical shock can cause severe personal injury or death; do not touch electrical wiring or components during testing.
Procedure
- Stop the generator set.
- Unplug the voltage regulator from the wiring harness.
- Using jumpers, connect a 12-volt battery to the F1/F2 terminals.
- Start the generator set and measure outputs at J4-4 - J4-6, L1 - L2, L1 - L0, L2 - L0, Q60 - Q1 (Q50-Q1 for 50 Hz), and S1 - S2.
- Compare readings: J4-4 - J4-6: 75 VAC 20; L1 - L2: 147 VAC 20; L1 - L0: 74 VAC 20; L2 - L0: 74 VAC 20; Q60 - Q1: 111 VAC 20; Q50 - Q1: 99 VAC 20; S1 - S2: 75 VAC 20.
- If these voltages are measured, the generator set is operating correctly and the problem is elsewhere.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 12 volts applied to F1/F2 should produce approximately 125 volts output at L1 and L2 with no load
Full service-parts list: Cummins/Onan HDKA →, Cummins/Onan HDKAQ →, Cummins/Onan HDKAR →
Source: Cummins/Onan 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.