toad1 Report post Posted June 29, 2016 My starting battery dies when the main house battery switch is on, whether on shore power or unplugged. With the switch off the start battery stays charged. All batteries charge with the engine running. All batteries are about three years old. I suspect the isolator, but cannot locate it, not sure if it even has one. On top of the start battery are two small boxes ( Hi Amp.,Buss 150 amp,. 181150F) I suspect they are circuit breakers, but have found them called isolators, circuit breakers or diodes ??? If they are circuit breakers and faulty,(open) I would have no power. ..... Where would an isolator be located? Any suggestions would be welcome. Share this post Link to post Share on other sites
wolfe10 Report post Posted June 29, 2016 Toad1, Welcome to the FMCA Forum. There are two types of battery isolators: Solenoid-base/relay based Diode based. Follow the large gauge wire from alternator B+ and you will find it. When the salesman switch is on, does the house battery bank die as well as chassis battery? Share this post Link to post Share on other sites
toad1 Report post Posted June 29, 2016 wolfe10 Thanks for your reply. I'm assuming that the "salesman switch" is the main battery switch located in the side door step well. In my 25 years of motor homing I have never heard that term But the house battery bank does not die, just the start battery. I will follow your suggestion and trace the alternator wire and hopefully it will lead me to the isolator. Share this post Link to post Share on other sites
dickandlois Report post Posted July 2, 2016 Toad1, The Buss 150 amp,. 181150F are high current circuit breakers. Has anyone done some work in the area around the battery cables and connections? Or have you had someone jumps start the coach? With the main battery switch off both the chassis and coach batteries hold a charge for days- Correct? Is the voltage level of the coach batteries enough to start the engine if you use the Aux. start switch? This link might help understand the wiring. but there are no circuit breakers pictured and the wiring shows a number of different systems. One should be close to how yours is setup. http://www.jamestowndistributors.com/userportal/pdfs/howtos/Tech_Battery_Isolator_Circuts.pdf The most common battery isolator is the one alternator, two battery unit. It doesn’t matter how many batteries are connected in parallel to the battery 1 or 2 terminal. A number of coaches do not have the isolator pictured. The positive side of one set of batteries is connected to one side of a relay and the second set to the other side. When the aux. start switch is energized the coach and house batteries are connected in parallel. They both charge from the Alternator because they are all connected in parallel. Rich. Share this post Link to post Share on other sites
