Skip to main content ↑ ↓
Topic: Charging problem (Read 453 times) previous topic - next topic

Charging problem

Looking for a little insight in diagnosing a charging issue.  2000 U270.  Started showing 11 volts and under on gauge on trip so I flipped boost switch and ran generator rest of way home.  Made it fine.  no issue.  Batteries were low when got home.  Charged chassis batteries back up with external charger and went to local shop in Tyler to check alternator and isolator.  They say alternator only putting out 12 volts and replaced.  On leaving shop I see gauge not reading any differently (around 11 volts) and have them look.  Say new alternator putting out 14 volts and checked it at batteries although they didn't check isolator( I am doubtful on this).  Get plug in aux port gauge to double-check and my dash gauge is pretty accurate(slightly lower (port gauge reads 11.87).  Moved alternator cable to chassis side of isolator to try and check it  and showing no charge when running at that post or at batteries or on any gauge.  Alternator never was working right after installed from what I can tell????    Excite wire???  Other??? 

Going back to complain tomorrow but thinking these guys know less or no more than me about my charging system design (claim to be motorhome specialists).  I don't see same voltage on house side and chassis side when boost switch flipped on at isolator terminals before I relocated alternator cable or after on any gauge.  Boost solenoid does appear to make click noise when I flip it on.  Over my head to figure this out.  Any help would be appreciated.

Re: Charging problem

Reply #1 –
Quote from: Popsicle59 –
They say alternator only putting out 12 volts and replaced.
Moved alternator cable to chassis side of isolator to try and check it  and showing no charge when running at that post...
Alternator never was working right after installed from what I can tell????    Excite wire???  Other??? 
We have heard this story many times on this Forum.  Of course, the first thought is that "they" did not wire the new alternator correctly.  It might be a missing or damaged "excite" wire or "sense" wire.  A few simple checks with a multimeter will help pin down the problem.  You can do the checks, or "they" can, but it sounds like you don't have much faith in "them".

Put alternator cable back on the alternator post of the isolator.  Boost switch OFF.  Run the engine at high idle for 10-15 minutes, then at normal idle check the following:
1.  Voltage at B+ (output) post on alternator.
2.  Voltage at alternator post on isolator.
3.  Voltage at chassis battery post on isolator.
4.  Voltage at house battery post on isolator.

Voltage at alternator B+ and at alternator post on isolator should be very close to the same...mid to high 14's.
Voltage at the two battery posts on the isolator should be about 0.7 volts less than the reading on the center post.

If the alternator is not putting out correct voltage, then you will have to tell us what make/model alternator they used as a replacement.  Better yet, also post a photo of the rear of the alternator so we can see all the terminals.  It is very common (due to unfamiliarity with diode isolators) for a shop to either install a new alternator that is not suitable for use on our Foretravel coaches, OR to improperly connect the alternator wires.  But we can't comment on that until we have the specs on the alternator.

Keep us informed of the results!

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Charging problem

Reply #2 –
They installed a Prestolite/Leece-Neville LN 2824 LC alternator.  Appears to have same connections as one replaced.  Getting 12.5 on house side and 12.1 on chassis side.  Alternator post is less than 10 but fluctuating a lot.  At alternator I have 11.59 on one small terminal and 12.1 on other.  Can't get a good read on B+ on alternator anywhere stable much less around 14.  I am going to go talk to the guys who did it and see if they can intelligently address it.  If not, I will move on to someone else.
/Users/bworthington/Downloads/IMG_2346.HEIC

Re: Charging problem

Reply #3 –
FWIW, check ALL of the connections for all of the wires. I fought a similar situation for 18 months. The solution was very simple: the sense wire was loose at the isolator. It looked good, so no one actually tugged on it. Eventually it fell off. Once it was back in place and tight all is good.

Re: Charging problem

Reply #4 –
Quote from: Popsicle59 –
They installed a Prestolite/Leece-Neville LN 2824 LC alternator. 
The alternator IGN (ignition) small terminal should be hot (12V) only when the ignition switch is in the ON position.

The alternator REMOTE SENSE small terminal should be connected either directly (at start battery POS post) or indirectly (at start battery post on isolator) to a source that always "sees" start battery voltage.

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Charging problem

Reply #5 –
Quote from: Popsicle59 –
They installed a Prestolite/Leece-Neville LN 2824 LC alternator.  I am going to go talk to the guys who did it and see if they can intelligently address it.
/Users/bworthington/Downloads/IMG_2346.HEIC
Why?  Follow Jeannies advice as there really are only three (four) wires that matter.  The big one goes to the center terminal if you have a diode isolator.  The small white one functionally works the same way as the red test lead on your multi meter and i goes to the chassis battery terminal on the isolator.  And the other one goes to a wire that has 12vdc when the ignition key is on and doesn't have 12VDC when the key is off.  It really is that simple.

IF you still have low voltage problems, come back and Jeannie will tell you where the magic adjusting screw is located.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Charging problem

Reply #6 –
Quote from: Old Toolmaker –
...Jeannie will tell you where the magic adjusting screw is located.
In my younger days, I would have snickered at the double entendre in that statement.

But alas, I grew up.  8)

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"
 

Re: Charging problem

Reply #7 –
Quote from: Chuck & Jeannie –
In my younger days, I would have snickered at the double entendre in that statement.
But alas, I grew up.  8)

Growing up is highly overrated. Never lose the inner child because it's the only way to see the world.

For instance: 
Dear Popsicle59,

If you're afraid of working with electricity because you might make a mistake, here's a little tidbit about your Leece Neville alternator.  Did you know that you can tie all three wires, output, IGN and S together at the positive terminal on your battery and all will be well?  But the IGN needs to be switched so that you don't drain your battery when the engine isn't running,  the "S" or sense wire is intended to adjust the output voltage so that it is correct at the battery, and the output goes to the positive terminal because if you connect it to the negative terminal you'll need another alternator.

Art Joly, Retired New England Toolmaker and antique auto restorer.

PS Notice the Oxford comma between battery, and, and.

1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.