Cummins/Onan — Testing AC Load Circuit Breaker - Voltage Drop Check
Testing & diagnosis
From a Cummins/Onan service manual covering: 4BT3.9-GC1, 4BT3.9-GC2, 6BT5.9-GC1, 6BT5.9-GC2, 6CT8.3-GS/GC1, 6CTA8.3-GS/GC1, 6CTA8.3-GS/GC2. Check it applies to your exact model before use.
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Before you start
- Contact with high voltage can cause severe injury or death.
Procedure
- Operate generator set with breaker in On position and load applied.
- Take voltage readings at line connections and load connections.
- Check for slight variation in voltage dropped across each pole.
- Unequal or excessive millivolt drops indicate contaminated contacts or loose connections.
- Stop generator set and disconnect battery negative cable.
Tools required
- voltmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Voltage drop should be slight and equal
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.