Battery light on

[BusterBus]

On a recent trip my battery light on the dash came on.  I started slowing down and it went off.  The volt gauge would show less
than normal as the rpm's went up but would increase to almost normal as the rpm's went down.  Fearing total battery discharge
I started the generator to hopefully keep the batteries charged.  When I started the generator the volt gauge would return to almost
normal.  I continued on to my destination without any problems, no battery light on and full running lights on.  I have a 2002 Allegro Bus with a 330 Caterpillar engine.  Any ideas on the problem and any solutions.

 

[BusterBus]

Clarification on above post:  Engine is a 3126 Caterpillar with 330 hp on a Freightliner Chassis.

 

[Molaker]

Sounds like an alternator/voltage regulator problem.

 

[Weewun]

Don't rule out a loose belt.  Increasing the RPM increases the charging voltage, hence additional drag of the Alternator, also running the Genny powers the converter thus supplying charging current to the batteries requiring less from the Alternator (less drag on the belt). 

 

[Gary RV_Wizard]

My vote is for the loose belt. It slips at higher RPMs or under greater load, then re-engages when you slow down a bit.

In any case, fix the simple things first.