Cummins/Onan — Testing Reactor CMR21
Testing & diagnosis
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Procedure
- Leads are marked 1, 2, 3 and 4. Wires 1-2 and 3-4 are wound on the same iron core.
- Measure resistance between 1-2 and 3-4.
- Resistance between 1-2 should be 0.38 to 0.39 ohms and between 3-4 should be 0.38 to 0.46 ohms at 77°F (25°C).
- Resistance between coils and from any terminal to reactor frame should be infinity.
Tools required
- ohmmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 0.38 to 0.39 ohms at 77°F (25°C)
- 0.38 to 0.46 ohms at 77°F (25°C)
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.