Battery disconnects and solenoids
A coach that's dead with a good battery often has a disconnect switch off or a solenoid that didn't latch.
The short version
- Find every battery disconnect: a switch at the door, a knob in the battery compartment, or a solenoid.
- Check voltage on both sides of the disconnect or solenoid. Battery on one side only means it's open.
- Latching solenoids need a pulse to change state. A weak battery may not be able to flip them.
- Lithium batteries may also be off at their own switch or asleep in the BMS.
Shop tip
Ask the customer if anyone stored the unit. Storage almost always means somebody turned the disconnect off.
Try it on a service call
Put the lesson to work on a hands-on troubleshooting case.
Keep going on 12V and batteries
Learn it
- Volts, amps and ohms, the simple way
- Voltage drop: the test that finds bad grounds
- Practice: find the bad connection
- Batteries: lead-acid vs lithium
- Fuses, breakers and grounds
Prove it
- Back lights are dim
- Battery dies even on shore power
- Lithium won't charge on cold mornings
- Coach is dead, battery is fine
- Batteries dead after storage