12v power for starting problem

[Dorn Hetzel]

I'm having an odd issue with my 77FC35.

Alternator seems generally OK, 14-ish volts when engine running.

Shore power DC supply seems maybe a little less ok but does seem to run all the lights, etc.


Can freshly charge main batteries which are three 12v batteries, two 950 cranking amps, one smaller, all parallel.
(This doesn't look like the original config (was that four 6v series parallel?) but it's how the bird came to me)


On fresh charge to main batteries with external charger/booster the engine will start fine,
but after either driving around for a while or sitting for a while on shore power, the mains seem unable to
start the engine. I have put two brand new 950 cranking amp batteries in within the last week, so I'm

pretty sure it's not the batteries.

If I connect the charger to the batteries, it says within a minute that they are full, but the engine won't crank
unless I use the booster, then it cranks fine.


Any thoughts on what the issue might be and how to diagnose further?

Regards,

Dorn Hetzel
77FC35
Hogansville, GA