Cummins/Onan — Testing the PMG
Testing & diagnosis · Permanent Magnet Generator
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan DQAD, Cummins/Onan DQAE, Cummins/Onan DQAF
Before you start
- HAZARDOUS VOLTAGE. Touching uninsulated parts inside the control housing and power output boxes can result in severe personal injury or death.
Procedure
- Disconnect plug J10 from the voltage regulator output stage module.
- Start the engine at the set and let the speed stabilize.
- Measure voltage across lead pairs J10-1 & J10-4, J10-4 & J10-5, and J10-5 & J10-1.
- Voltage should be at least 150 VAC for 50 Hz sets and at least 180 VAC for 60 Hz sets.
- Voltages should be approximately the same for each set of leads.
- Stop the set and measure resistance across the same lead pairs.
- Refer to Table 6-3 for resistance values and Generator Reassembly for frame size.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- At least 150 VAC for 50 Hz sets
- At least 180 VAC for 60 Hz sets
- PMG stator resistance: HC4 = 2 ohms; HC5/HC6/HC7 = 6 ohms
Full service-parts list: Cummins/Onan DQAD →, Cummins/Onan DQAE →, Cummins/Onan DQAF →
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.