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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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Re: low volts revisited
Reply #16
Thanks everyone for sharing.  Finally got it sorted out, took Cascade Diesel and RV in Northbend Wa to find "Pilot Error".  I had replaced the battery isolator, which I am pretty sure was bad and the boost solenoid which I am pretty sure was bad,...

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  • John44
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Re: low volts revisited
Reply #17
Just remember to use the load tester sparingly,it puts aload on the battery.

Re: low volts revisited
Reply #18
Cascade connected...a ground wire to the boost sol. and all works as it should.

...the boost sol. did not have a ground wire when I took it off. 
Is the new boost solenoid a "4...

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Re: low volts revisited
Reply #19
4 post, but it only had one small post wired when I removed it.  it is working now but diagram 2126 is not real clear on this part.

Re: low volts revisited
Reply #20
4 post, but it only had one small post wired when I removed it.
Perhaps that is why it wasn't working.  May have been good all the time, but just wired incorrectly.

Easy to test a...

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Re: low volts revisited
Reply #21
still wasn't getting power from the new alt. so took it off and had it bench tested and it was fine.  nor was I getting any response from the new boost sol. 

  I will take some...


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Re: low volts revisited
Reply #22
"Boost solenoids" come in two flavors, intermittent and continuous.  And 3-terminal or -4.
Unless you want to go with a solid state solenoid or a latching solenoid (draws no current when in...

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