Originally Posted by javelin
Hi. Not sure I understand what operating the emergency start switch during your headlight test was supposed to do.......brighten the head lights I assume, if the house batteries were fully charged while chassis battery was not? Does your coach use the BIRD battery control system? If yes, I have attached a basic BIRD schematic for reference. If the interconnect (isolator) relay operates when emergency start button is operated, it ties the coach and chassis batteries together and should have no directional current limitations. Of course when both coach and chassis batteries are dead the interconnect (isolator) relay wont operate either.
That was my Point, leave the headlights on for a while to draw down the Chassis battery partially, then try the switch, the isolator should connect the batteries and the headlights get brighter. If not, then the isolator isn't working. Personally I just placed a volt meter across the coach battery, with the chassis battery drawn down some, and the headlights on. there should be a small voltage drop when the isolator connects, which there wasn't.