RV Repair: 1993 Gulfstream electrical problem, cummins turbo diesel, diesel pusher

Question
I am trying to help a friend fix an electrical issue.  He has a 1993 Gulfstream Scenic Cruiser.  It’s a 33 foot diesel pusher built on a Spartan chassis with a Cummins turbo diesel and an Allison transmission.  The specific problem occurs when he am hooked up to “shore” power.  There is a large solenoid on the chassis which serves to engage all 4 batteries (chassis and coach) when a toggle switch is thrown while starting.  While hooked up to shore power this solenoid engages and releases every 30 to 60 seconds on its own.  He replaced the main power inverter and that did not stop the problem.  A year or so back he also replaced the solenoid and it did not solve the problem.  He put a 12 volt test light on the two light wires leading to the solenoid.  On one of the wires the test light glows very dully.  It appears he has a constant low voltage getting to the solenoid which seems to build in the solenoid until it actuates, also causing the batteries to drain while sitting between roadtrips.

Answer
electrical issues like this are tough to follow and find the problem.  Check for a good clean, ground.  If this does not clear the problem.  The easiest way is to first run new wires from the solenoid to the switch.  Disconnect the wires at each end and run new ones. The existing wire could be chaffed somewhere or some other connection problem.  If you can't find it with in 15 minutes, go ahead and replace the wires.

Garry