Originally Posted by niceguy9605
Does anyone know some facts about the Battery Isolator Relay or Big Boy on a 06 HR Navigator 45PDQ? What does it do? And, when do I know if it is going out? ANY info would be helpful.
This write up was done by the owner of an '04 Executive so should be correct for your coach:
Your coach has the same BB system as mine. The Big Boy Relay is controlled by Bird Relay which is located in the RRB. It is located on the right side and is the third circuit board from the top. There is a Green LED-(ISO Relay On)-third from the top on the board that should be Illuminated and the Big Boy Relay should have a low humm and be hot to touch when working properly.
When you disconnect from shore power and the generator is not running, the Green LED should be out. The Big Boy Relay will drop out of the circuit when the dc voltage drops to 12.5 to 12.8 vdc when measured at the Battery side of the Big Boy Relay.
When connected to shore power or when the generator is running you should have power to the #2 pin on the eight pin connector on the right side of the board. The #1 pin is ground and the #3 pin is powered on when you turn on the Ignition Switch. Pin #4 is from the battery boost circuit, Pin #5 is the Domestic power circuit. Pins #6 & #7 are blank. Pin #8 is a ground circuit.
The six pin connector on the top of the board powers up the relays. The left pin is Pin #1 and is ground, Pin #2 powers up the Big Boy Relay, Pins #3-4-5-6 power up the two Domestic Relays to the right of the Big Boy Relay. When working properly you should measure about + or - 4.6vdc on Pin #1 when the Board is powered up and the Big Boy Relay is working.
If the BB is powered up and running correctly, you should have around 4.5 to 4.8 vdc on pin 1 of the 6 pin connector. You should also have that same voltage on pins 1, 4, 5 & 8 on the 8 pin connector.
On the BB Solenoid you should be seeing 12.8+ vdc on the chassis side battery post-(left side) and 13.0+ vdc on the house battery side post-(right side). A differential of .3 to .6 vdc between these two posts is normal.
If your Inverter is set up correctly and the Bird relay is working-(green light on) the Inverter through the BIRD Relay and the BB will charge the Coach Batteries first and then the Chassis batteries and when all the Batteries are fully charged the Inverter will go into float charge. When plugged into Shore Power or with the Genset running the Green LED will be Lit on the BIRD Relay Circuit Board, If not I would venture to guess that the circuit board is failing or has failed. The relay above the eight pin connector on the BIRD circuit board controls the Big Boy Relay, it could be failing.
Full time since '07