Cummins/Onan — PMA Tests
Testing & diagnosis · PMA (Permanent Magnet Alternator)
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan HDZAA
Before you start
- Hitting the rotor or prying against it to remove it can break the magnets inside.
Procedure
- Disconnect the 9-pin connector on the inverter and measure main winding resistance between pins 1 and 2, 2 and 3, 3 and 1. Replace the stator if any winding is grounded or open or does not measure 1.1
- With the 9-pin connector disconnected, measure auxiliary winding resistance between pins 4 and 9. Replace the stator if grounded, open or not 0.3 ohms within 10 percent.
- Disconnect the 6-pin connector from the internal control panel and measure auxiliary winding resistance between pins 2 and 3. Replace the stator if grounded, open or not 0.3 ohms within 10 percent.
Tools required
- Ohmmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Main winding 1.1 ohms within 10 percent
- Auxiliary winding 0.3 ohms within 10 percent
Full service-parts list: Cummins/Onan HDZAA →
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.