Coachmen Mirada 2004 House Battery wont charge from Engine

[blackwell99]

Hi,
Our Coachmen Mirada wont charge the House Battery from the Engine.
Charges fine from shore power. I did a lot of searching on forums about
this problem and its clear there is an isolation solenoid or relay that disconnects the house battery from the engine when the engine is not running or when your on shore power.

Does anyone have electrical diagrams for this RV? There are several solenoids and relays under the front step but I'm having a hard isolating the
problem.

Thank you,
Mike

[garyspang]

Check for 12 volts on the coil (small) terminals when the engine is running, and zero volts when ignition key is withdrawn.

Across the large posts there may be 0.1 or0.2 volts with the ignition off and the contacts are open. This is the slight difference in the house battery voltage and the starter battery voltage.
With the engine running this should drop to 0.0 volts because the solenoid contacts are closed. Anything else indicates the relay plunger is frozen from an internal plastic meltdown and the contact can not close.

Mine has failed for the second time (130,000 mi) from internal meltdown from exessive heat. the old cold coil measures 10 ohms, the replacement measures 15 ohms. This will acount for 6.3 watts less heat at 14 volts and I hope it will last longer. When I go back into the MH, Iwill send you the part number, unless I forget.