Cummins/Onan 1750DQKB / 3200 Series — Testing the PMG
Testing & diagnosis · Permanent magnet generator (PMG)
For the Cummins/Onan 1750DQKB / 3200 Series, from the Cummins/Onan service manual.
Applies to: Cummins/Onan 1750DQKB, Cummins/Onan DFE
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.
- If voltages are low or uneven, check all leads and connections before disassembling the PMG.
- Stop the set and measure electrical resistance across the lead pairs with a Wheatstone bridge or digital ohmmeter.
- Each winding should have a resistance of approximately 2.6 ohms.
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
- approximately 2.6 ohms per winding
Full service-parts list: Cummins/Onan 1750DQKB →, Cummins/Onan DFE →
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.