[A/S] Overlander electrical problem Need Help

[SHMossLanding@xxxxxxx]

When i hooked up this weekend,  I had a breaker start popping.  It is the 24 
AMP breaker that is tied between the charge line from the pigtail to the 
brakeaway switch. I pulled the breaker out and had it checked. It's OK.  I 
have continuity from the pigtail to the rear panel in the coach. If I connect 
the coach battery and plug the pigtail in the tow vehicle, the breaker pops 
on and off.  If I disconnect the coach battery and plug the pigtail in no 
popping.  If I connect the two battery cables in the coach togather, are the 
lights etc. supposed to work?  All systems work on just the coach battery.   
Does anyone have an idea where else to look for the problem?
                         
                                                                         
Thanks,
                                                                         
Chuck & Lynn
                                                                         1965 
Overlander