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Alternator Charging Problems

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Charles Burden:
I have a few questions.  Tim are you talking about the "coach" batteries decreasing in charge as you travel down the road?  OR Are you talking about the "chassis" battery decreasing?  The reason I ask is that it sounds like you have to use the generator to charge the "coach" batteries because the alternator is not doing it.  If I am getting close please let me know because I had a similar problem.

Sometimes on coaches there is a battery isolation relay device (BIRD) that keeps the two sets of batteries separated purposefully.  This is so the use of the coach batteries do not discharge the chassis batteries while you are dry camping and leave you unable to start your engine or generator.  Conversely when you are in a campground your "shore" power is supposed to charge up your coach batteries and when they reach a preset charge level (13.4 or so) the relay allows the batteries to connect to each other so the chassis batteries can be maintained fully charged.  When traveling down the road the alternator is supposed to charge the coach batteries.  

If this is not occurring your BIRD or BIG BOY solenoid may not be operating properly.  

Tim Bentley:
It seems to be the coach batteries that are not charging.  The problem is intermittent so if is difficult to tell.  I thought about the big boy, that may be the problem.  I.m home now so there is not hurry but I think I will replace the alternator and see if the solves the problem. If that doesn't work I'll look at the big boy

Charles Burden:
Is this a new problem or has this been the case since you got the RV?

On our coach the circuit board that controls the BIRD and Big Boy has a plastic plug with the wires in the plug.  The technician found that the + and - leads were reversed.  Once changed the system charges the coach while riding and the chassis on shore power.  This wiring error was from the factory and had been this way for almost a year while at the dealer.    

Tim Bentley Co-Admin:
This is a new problem. The coach has 90000 miles on it and is on its second alternator.

Tim Bentley:
Had the alternator rebuilt, that costs $250 in San Diego.  I would have tried rebuilding it  myself but I could not even get the drive pulley off.  The rebuilt alternator in installed and it looks like the problem is solved.  The charge rate is 14.2 volts and seems to be holding steady but won't no for sure until my first trip,  

Thank you for all your help and suggestions.

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