RV Repair: battery issues, 5th wheel trailer, 12 volt batteries

Question
QUESTION: I have a 1984 prowler regal 5th wheel trailer that has two 12 volt batteries, a converter and AC power cord with breaker box.  I was having problems with the electric jack motor not running and thought it was a battery issue.  I have replaced both of the 12 volt batteries with new ones.  When the first battery was connected I had power inside the trailer.  When the second battery gets hooked up the power inside is gone.  Also the electric jack motor only runs when the second battery is connected. My manual shows a wiring diagram that shows a 30 A in line fuse coming off the positive post of a battery (unfortunately my book only shows one battery not two).  In our trailer the fuse is on the second battery.  It appears to be fine.  The book also shows a 30A breaker connecting into that line.  Question 1:  do you know where we can find the breaker?  it is not apparent to us and we have looked everywhere.  Question 2:  do you know what the problem could be and is it something other than the breaker we are thinking it could be?  Thank you for any help you can give me

ANSWER: the manual is for all campers, and not all have electric jacks.  The electric jack requires its own battery.  So that is a separate circuit.  Since the jack works good, that circuit is good.  The 30A fuse is to protect the jack motor.  

The first circuit, has a breaker rather than a fuse.  This breaker may be located in the converter.  On some RV's the converter takes over as soon as the AC power plug is unplugged.  and give control over to the AC circuit when the plug is plugged in.  sometimes in this case, the AC power has to be plugged in  then unplugged to enact the DC converter.  do the lights work on AC power?  It is possible the battery connections were disturbed when the second battery was hooked up.  Where is the first circuit getting it's ground?  Possible the battery converter is the problem.  Look on the converter for a triped 30A button....may be popped out.  

Good Luck!

---------- FOLLOW-UP ----------

QUESTION: We have unhooked everything and started again.  Now things are working and then suddenly stop.  Is it possible that the ground wire connection could be the cause of our problem?  It is currently connected to a thin sheet of metal that does not appear very solid.  Perhaps it is vibrating loose.  Would a loose ground wire cause faults in the system?

Answer
Absolutely a ground can be the cause.  You can buy a braided cable for grounding car motors from an auto parts store.  This is a great grounding cable.  You should ground that to something very solid and condcutive...like the frame.  Can not have too much ground.  Good luck.