Special Motor Home Technical Information

This is a collection of special technical information for servicing Class A Diesel Motor homes.

The Battery Control Center provides the circuitry for charging your engine and coach batteries for all of the operating modes (shore power, generator and engine alternator).  It is a complex unit with a number of time delays and protection schemes designed into the digital circuitry.  Several circuit breakers, relays and 18 fuse positions are used inthis box.  It is designed to always protect the engine battery in order to ensure it has sufficient power to start the motor home.  A very large solenoid switch is included (fondly referred to as the ‘Big Boy’) which couples the engine and coach batteries together for charging.  It is usually mounted on the wall in the battery compartment.

Battery Control Center


The Transfer Relay provides the A/C switch to automatically change from shore power to generator power.  It is normally in the shore power position.  When the generator output voltage is provided to the relay it switches to the generator.  This is a 50 amp rated relay which switches four contacts simultaneously.  The contacts can get burned over time and occasionally the heavy wires can work loose.  Keep the contacts clean and check the connections on a yearly basis.

Transfer Relay Service


The Energy Management System provides an automatic monitoring and control system for all of your A/C appliances.  It monitors the input ampere capability of your shore power source (20, 30, 50).  If you exceed the input power source it will automatically turn off appliances before you trip any circuit breakers.  Once the load is reduced the appliance will resume operation.  For example, if you are on a 30 amp circuit and your air conditioner (A-C) is running, if you turn on the microwave the air A-C will temporarily turn off.  The appliance priority (what turns off first) is selectable.

Energy Management Center