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low volts revisited
only getting 12-12.3 volts from chassis battery.  replaced isolator, cleaned terminals and islolator connections, batteries are 2.5 yrs old and alternator is also 2-3 yrs old.  no change when I plug into shore power but readings is at 13.5-14...

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  • Rudy
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  • Commercial Member
Re: low volts revisited
Reply #1
Dale,  There is no charging of the chasis battery when plugged into shore powere on the coach as delivered from Foretravel.  Many owners have added chasis battery charging devices to their coaches.  Sounds like you might be wanting to do so too.

I...

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Re: low volts revisited
Reply #2
Thanks Rudy.  I kind of thought the shore power would not charge the chassis battery but the volts shlould be 13+ running down the road but i am not getting more than 12-12.3    Alternator?  what do i test?

Re: low volts revisited
Reply #3
Alternator, battery isolator or wiring issue (assuming monitors are accurate-- again, digital voltmeter reading at the battery is most accurate).

And checks with the voltmeter at alternator B+ and each terminal of the battery isolator with the...

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Re: low volts revisited
Reply #4
thanks Brett.  Chassis battery on volt meter at the battery is 12-12.3   trying to get a measure off the alternator and get nothing.  going to try the isolator and alt-B test.  will report back.

Re: low volts revisited
Reply #5
With engine at 1,100 RPM or so, assuming diode-based BATTERY ISOLATOR, connections good and batteries reasonably charged/not deeply discharged:

B+ alternator to good ground high 13's to low 14's VDC

Center post diode-based battery isolator= same...

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Re: low volts revisited
Reply #6
Chassis battery is charged on shore power by onboard charger, starting battery can be charged on shore power by same onboard charger if the boost switch on dash is on.  All batteries are charged by alternator.  I agree checking the battery...

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  • Rudy
  • [*]
  • Commercial Member
Re: low volts revisited
Reply #7
Mr. Pat,  I was referring to the main engine starting batteries as "Chassis Batteries".  The other bank of batteries would be the house batteries which are the shore power charged bank.

Hope this helps one know which bank I was referring to.  All...

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Re: low volts revisited
Reply #8
I have run out of time today so will have to table the project for later.  tried to get measure at the alt and isolator but could not get a reading on my voltmeter.  I know it works because i got readings off both banks of batteries.  either i am...

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Re: low volts revisited
Reply #9
Dale,

You state that the alternator is 2-3 years old.  So did they install the correct alternator?  OEM you had a DUVAC alternator and some shops don't deal with this type of system. So you could have a good alternator that does not know it is...

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Re: low volts revisited
Reply #10
Terminology:

Chassis battery starts the engine.

House battery provides house functions.


  • Twig
  • [*][*][*][*][*]
Re: low volts revisited
Reply #11
Take a long wire. Doesn't matter what size, it's a test. Bolt one end to the + connector of the alternator. Attach the other end to the + post of the START (never could understand why anyone would call it a chassis if it STARTS the vehicle)...

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Re: low volts revisited
Reply #12
Take a long wire. Doesn't matter what size, it's a test. Bolt one end to the + connector of the alternator. Attach the other end to the + post of the START (never could understand why anyone would...


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  • Twig
  • [*][*][*][*][*]
Re: low volts revisited
Reply #13
Actually, it could be little more complicated than that.  Remember, most of these alternators are not "simple".  This assumes the sense wire and if present the ign terminal have proper...


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Re: low volts revisited
Reply #14
Dale you cannot check the alternator out put at the batteries.. checking at the batteries will give you battery voltage only if alt is not putting out.

Re: low volts revisited
Reply #15
Dale you cannot check the alternator out put at the batteries.. checking at the batteries will give you battery voltage only if alt is not putting out.

Actually, checking at the batteries is...

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