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Cummins ISC 330 with 160a alternator. I had a suspicion from my last start that the chassis batteries weren’t charged fully. I’m not good about watching my gauges so didn’t have an idea of a problem before noticing this. I don’t have an ammeter but do have a chassis voltage gauge. Decided to run the engine for a test. First I checked the chassis batteries with a voltmeter and they were just barely over 13v. When I turned the key on the panel voltage showed a little more than 12v.  I started the engine. Seemed to crank good but it took about 5 seconds for the voltage to move off 12v and indicate charging at about 13.3-13.5 volts. (Difficult to tell since the gauge is in single digit increments. One of my old engineering professors would say you can’t resolve it closer than one volt.) It showed 13+ For about 15 seconds the went back to about 12v for 5 seconds then 13+ again for about 15 seconds. I hit my stop watch to see if it maintained this regularity and it did for about 6-8 cycles thenit went steady at 13+v for a couple of minutes before I turned the engine off.

The next day I had to move the coach to a new site. The voltage went through the same process, about six 20 second cycles then stabilizing at 13.3-13.5v for the ten minutes it took to move.

We are near Denver for now but had planned to go to the mountains for some boondocking to test my new solar installation but with this issue I decided it would be prudent to have the charging system checked out. Of course it was a Friday afternoon so finding a shop was difficult. Luckily I was able to schedule an appointment for Monday morning at a local diesel shop.

Does anyone have any insight about this issue? 
Ed         
‘05 HR Ambassador 

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The alternator should be putting out 14+ volts with the engine running. mine reads about 14.3 VDC.

13+ to me indicates that possibly you have a failed diode and it may be on its last leg.

Don't like analog gauges. I use SilverLeaf to monitor all of my engine vitals.

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48 minutes ago, saflyer said:

Cummins ISC 330 with 160a alternator. I had a suspicion from my last start that the chassis batteries weren’t charged fully. I’m not good about watching my gauges so didn’t have an idea of a problem before noticing this. I don’t have an ammeter but do have a chassis voltage gauge. Decided to run the engine for a test. First I checked the chassis batteries with a voltmeter and they were just barely over 13v. When I turned the key on the panel voltage showed a little more than 12v.  I started the engine. Seemed to crank good but it took about 5 seconds for the voltage to move off 12v and indicate charging at about 13.3-13.5 volts. (Difficult to tell since the gauge is in single digit increments. One of my old engineering professors would say you can’t resolve it closer than one volt.) It showed 13+ For about 15 seconds the went back to about 12v for 5 seconds then 13+ again for about 15 seconds. I hit my stop watch to see if it maintained this regularity and it did for about 6-8 cycles thenit went steady at 13+v for a couple of minutes before I turned the engine off.

The next day I had to move the coach to a new site. The voltage went through the same process, about six 20 second cycles then stabilizing at 13.3-13.5v for the ten minutes it took to move.

We are near Denver for now but had planned to go to the mountains for some boondocking to test my new solar installation but with this issue I decided it would be prudent to have the charging system checked out. Of course it was a Friday afternoon so finding a shop was difficult. Luckily I was able to schedule an appointment for Monday morning at a local diesel shop.

Does anyone have any insight about this issue? 
Ed         
‘05 HR Ambassador 

The voltage swings that you are observing when starting a cold engine are your plate heater cycling on and off, this is a normal occurrence.

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11 minutes ago, Dr4Film said:

The alternator should be putting out 14+ volts with the engine running. mine reads about 14.3 VDC.

13+ to me indicates that possibly you have a failed diode and it may be on its last leg.

Don't like analog gauges. I use SilverLeaf to monitor all of my engine vitals.

I forgot there is digital voltage readout but not an amperage one in my ScanGuage D. Tried the test again. It did about 5 cycles of 12.1v for 4 or 5 seconds then 13.7-13.9v for about 15 seconds. Eventually it settled to reading 13.9-14.0 v with an occasional 14.1v. Does that still indicate a problem?

What is a SilverLeaf?

Thanks,       
Ed

 

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2 minutes ago, saflyer said:

I forgot there is digital voltage readout but not an amperage one in my ScanGuage D. Tried the test again. It did about 5 cycles of 12.1v for 4 or 5 seconds then 13.7-13.9v for about 15 seconds. Eventually it settled to reading 13.9-14.0 v with an occasional 14.1v. Does that still indicate a problem?

What is a SilverLeaf?

Thanks,       
Ed

 

Since your ScanGauge is reading over 14+ volts I believe you are OK. I also agree with the previous poster that the initial fluctuation is from your Grid heaters which turn off after the air intake has reached temp.

SilverLeaf VMSpc is an add-on system which connects to the engine diagnostic port and takes all of the ECM information and displays it on a computer screen in the format that I create.

https://www.silverleafelectronics.com/node/6

 

VMSpc-14.JPG

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On 8/22/2021 at 9:19 AM, Dr4Film said:

The alternator should be putting out 14+ volts with the engine running. mine reads about 14.3 VDC.

13+ to me indicates that possibly you have a failed diode and it may be on its last leg.

Don't like analog gauges. I use SilverLeaf to monitor all of my engine vitals.

Jeez, I thought 14+ sounded proper. My '03 Exec has never shown more than 13.5v (4 years running) with the engine running reading my BlueFire and putting DVM across the engine batteries. You mentioned bad diodes. Is that something a hack could do or would it be a trip to a specialty shop? FWIW: My dash gauge has never been accurate and measures 12v with the engine running (I gave up chasing that problem). The batteries seem fine and are always charged. 

Interesting side note to the techies out there. I chased a low voltage reading for days on my '18 Camaro. It typically hovers around 12v. I even insisted that the alternator be replaced under warranty. Hmmm same deal. Finally a service manger explained to me the operation of VARIABLE ALTERNATORS. Ahh crap something else to save fuel. They don't call for a full charge current unless the battery capacity drops below 12v. Seems like a good way to eat batteries to me. I liked the old 14v+ method. 

 

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3 hours ago, Grampy OG said:

Interesting side note to the techies out there. I chased a low voltage reading for days on my '18 Camaro. It typically hovers around 12v. I even insisted that the alternator be replaced under warranty. Hmmm same deal. Finally a service manger explained to me the operation of VARIABLE ALTERNATORS. Ahh crap something else to save fuel. They don't call for a full charge current unless the battery capacity drops below 12v. Seems like a good way to eat batteries to me. I liked the old 14v+ method. 

Would that be the new “smart alternators”?

 

3 hours ago, Grampy OG said:

Jeez, I thought 14+ sounded proper. My '03 Exec has never shown more than 13.5v (4 years running) with the engine running reading my BlueFire and putting DVM across the engine batteries. 
 

Is the BlueFire anything like the ScanGaugeD and the SilverLeaf hooked up to the OBD port?

Along that line would a readout from the OBD port be subject to the voltage drops of the dash gauge?

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9 hours ago, saflyer said:

 

Yes smart alternator, however that is not the case with an '03 Monaco Executive. 

The BlueFire does hook to the ODB/DATA (like a ScanGauge or Silverleaf) port on the coach. The data comes directly from the engine computer so in my opinion is much more accurate than any analog dash gauges. Back in '03 the Dynasty, Exec, Sig coaches had a system built into the backup monitor that was called Trip Tek. TT preceded Aladin and was much more simplistic. TT also reads the ECU directly and the numbers match what I get on the BlueFire. The BlueFire is just faster to read because I can see all of the data on one screen instead of paging through the multiple pages that TT presents. 

All that being said my alternator still only puts out 13.5 volts and I am wondering if it is just another failure waiting to happen. 

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23 hours ago, Grampy OG said:

Yes smart alternator, however that is not the case with an '03 Monaco Executive. 

The BlueFire does hook to the ODB/DATA (like a ScanGauge or Silverleaf) port on the coach. The data comes directly from the engine computer so in my opinion is much more accurate than any analog dash gauges. Back in '03 the Dynasty, Exec, Sig coaches had a system built into the backup monitor that was called Trip Tek. TT preceded Aladin and was much more simplistic. TT also reads the ECU directly and the numbers match what I get on the BlueFire. The BlueFire is just faster to read because I can see all of the data on one screen instead of paging through the multiple pages that TT presents. 

All that being said my alternator still only puts out 13.5 volts and I am wondering if it is just another failure waiting to happen. 

Some alternators have an adjustment on the regulator to set the output voltage.

Replacing the diodes is not a DIY job for most, as these things can be difficult to put together and get the brushes in the right position without some special tools and techniques.
Once you verify it is an alternator problem, best to remove it and take it to a local rebuilder.  Reman alternators may not match the original.

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2 hours ago, dl_racing427 said:

Some alternators have an adjustment on the regulator to set the output voltage.

Replacing the diodes is not a DIY job for most, as these things can be difficult to put together and get the brushes in the right position without some special tools and techniques.
Once you verify it is an alternator problem, best to remove it and take it to a local rebuilder.  Reman alternators may not match the original.

Thanks very much

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