Cummins/Onan — Testing The Float Switch Assembly
Testing & diagnosis · Day tank float switch assembly
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan DFAA, Cummins/Onan DFAB, Cummins/Onan DFAC, Cummins/Onan DFBF, Cummins/Onan DFCB, Cummins/Onan DFCC, Cummins/Onan DFCE, Cummins/Onan DFE
Procedure
- Remove the fuel pump control cover, disconnect the wiring jack and unscrew the assembly from the top of the day tank.
- With an ohmmeter, test for continuity (switch closed) between each pair of colored leads while holding the assembly vertical.
- Replace the assembly if any switch is open (all readings should be zero).
- Lift each float in turn to 1/8 inch (3 mm) below the C-clip stop above it using a feeler gauge.
- Test for electrical continuity; replace the assembly if any switch does not open (all readings should be infinity).
- Use pipe thread sealant when replacing the assembly.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- All switches closed readings should be zero.
- All switches open readings should be infinity.
- Float lift 1/8 inch (3 mm) below C-clip stop.
Full service-parts list: Cummins/Onan DFBF →, Cummins/Onan DFCC →, Cummins/Onan DFCE →, 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.