Author Topic: Not charging  (Read 6039 times)

0 Members and 1 Guest are viewing this topic.

Offline RLS

  • Newbie
  • *
  • Posts: 41
Not charging
« on: January 24, 2016, 03:09:32 PM »
Have a 06 Meridian with a C7. Went to get get ready to head south and its and not charging. Check info Ctr light came on voltage was showing 11.8 bouncing up and down to 12. 4 or 5. Took to local Freightliner dealer, they replaced the alternator. Drove home started acting up again took back to Freightliner dealer. They trouble shot thought was a bad cable from alt to batt. Added a second line Gage 3 wire. Drove home noticed that as I accelerating the voltage would drop. The faster I went the lower it went, at cruising speed about 62/63 voltage would be in the low 12s . If I let off the gas  it would climb back up to around 13 volts. Call Freightliner back up, they thought it might be a slipping belt, went back and got a new belt, replaced belt. No improvement. Anyone have any ideas?

Offline ziggyh

  • Full Member
  • ***
  • Posts: 202
Re: Not charging
« Reply #1 on: January 24, 2016, 03:34:06 PM »
Do you know what brand of alternator or can see a part number.

If it is a leeche alternator their should be a plug on the back with 2 wires one connects to the output terminal and the other should go back to a relay/fuse block. It should have 12 +volts when the engine is running. This wire wakes up the alternator to start it charging. This wire is usually fused so be sure to check the fuses and the connections at the batteries.  Some systems use a relay for this circuit as well.

Wiring diagrams are a great help, if one is available.
ZiggyH

2007 Revolution LE
C9

Offline RLS

  • Newbie
  • *
  • Posts: 41
Re: Not charging
« Reply #2 on: January 24, 2016, 03:48:24 PM »
I will check what alternator brand tomorrow. I had cleaned the batt terminals before I took to Freighliner.  Don't have a wiring dia. Will try to trace wiring tomorrow and see what I can find. Thank you.

Offline WILDEBILL308

  • Full Member
  • ***
  • Posts: 103
Re: Not charging
« Reply #3 on: January 24, 2016, 07:44:01 PM »
I would be back at Freightliner.
Bill
2003 Bounder 38N,300 HP 5.9 Cummins
Allison 3000MH Trans.Towing 2014 Honda CRV. Home base Fort Worth, Texas
A man who carries a cat by the tail learns something he can learn in no other way.
-Mark Twain-

Offline Brett Wolfe

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 2497
Re: Not charging
« Reply #4 on: January 25, 2016, 05:44:54 AM »
Many times, an RV alternator is DIFFERENT than one on a truck. Guys working on trucks most of the time often do not know this.

Sure, all alternators have a B+ terminal for positive OUT

Many have a separate ground lug while others ground through their physical connection to the engine

But, few truck alternators have an external sense terminal.  This is critical if you have a diode-based battery isolator, as there is a .7 VDC drop in voltage across the isolator (it is turned into heat in the isolator-- that is why the large aluminum fins to dissipate the heat).

Additionally, some alternators have an "excite" terminal that is hot only when the ignition is on.

Make absolutely certain that the new alternator has the same features as the OE AND that it is wired properly.

BTW, you have a serpentine belt and automatic tensioner that "powers" the alternator as well as other accessories.  So belt slipping would be very unlikely unless the belt or automatic tensioner have failed.  In other words, slipping is unusual.

Offline RLS

  • Newbie
  • *
  • Posts: 41
Re: Not charging
« Reply #5 on: January 25, 2016, 04:56:00 PM »
Found the problem. The mechanic that installed the alternator did not tighten the nut on the ground. I tightened it and all is fine.

Offline ziggyh

  • Full Member
  • ***
  • Posts: 202
Re: Not charging
« Reply #6 on: January 25, 2016, 06:27:00 PM »
Great,  Always nice to hear the end result.
ZiggyH

2007 Revolution LE
C9

Offline Mike Groves

  • Newbie
  • *
  • Posts: 1
Re: Not charging
« Reply #7 on: February 02, 2016, 07:24:23 AM »
Brett,

Curious about the .7V drop across the isolator.  I have had alternator issues.  In 2014 just before a trip across country I had my alternator on a '99 Beaver Marquis C-12 rebuilt and it was showing 14.7 volts on my computer.  Went across country and started back and my alternator failed.  At a shop the guys told me that "on the bench" my again rebuilt alternator showed normal voltage output of 14.2 (which they said was correct for the Leece Neville unit), but when they put it in the coach it was going to 15.8 plus and they couldn't explain it but felt it would burn itself up as it was outputting beyond specs.  To keep it down to 14.2 they crafted some soft of cable hookup at the alternator using diodes which limited the alternator to 14.2 but my computer never goes above 13.2V (1 Volt less than normal) so I wondered where I am losing that volt. 

You said the drop across the isolator would be about .7V so that would account for much of it, and might also explain why with no limiting diode cable that it was overcharging (which is why this shop said it simply burned up).

I've been using it as installed (but haven't put on nearly the miles) since May of 2014 without a problem.  It continues to show 12.8 to 13.2V as I run down the road, and I thought of replacing the isolator.  Might that still be a good idea?  What else is between the alternator and my chassis batteries besides the isolator?  I get 14.2V at the alternator but as the computer tells me and as I've measured at the battery, only 13.2V.

Mike Portland, Oregon

Offline Brett Wolfe

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 2497
Re: Not charging
« Reply #8 on: February 02, 2016, 02:21:19 PM »
Mike,

Sadly there is little consistency in how alternators/batteries are wired.

But, if you have a diode-based isolator (vs solenoid based isolator) then you will have a REMOTE SENSE terminal on the alternator and a small gauge wire going to the "chassis battery side" of the diode-based isolator.  It can go to the chassis battery lug of the isolator, the chassis battery positive terminal itself or any connection between the two. 

Now, if there is any resistance in the sense wire or its connections, it falsely "reports" lower than actual battery voltage to the alternator.  Start by checking for clean and tight connections at both ends of the sense wire.  Voltage at the chassis battery should be 14.0-14.2 VDC with engine running at above idle speed.  So, common for alternator to be .7 VDC higher.

Brett


Offline ziggyh

  • Full Member
  • ***
  • Posts: 202
Re: Not charging
« Reply #9 on: February 02, 2016, 03:42:01 PM »
I find that an easy way to check for resistance or voltage drops in electrical circuits is to measure the voltage at the start of a circuit to the end.  So as Brett indicated to check the sense wire and connections for resistance put one lead of the volt meter at the alternator connection and the other lead at the location where that wire goes. You must measure with the circuit active to get a reading or in this case engine running.  Any electrical circuit can be checked this way as long as it is always loaded to get a reading. 

The ground side of circuits is often overlooked and equally as important as the power side, and is measured the same way.

All the voltage drops in a circuit will equal the source voltage.  All circuits will have some voltage drops that come from the size and length of the wires, number of connections and quality of them.

Attached is a picture of a voltage drop over the alternator output wire to the Positive battery and the negative side.

With the engine running at idle, headlamps on and
blower on high, measure the voltage drop between
generator B+  circuit and the positive battery terminal.



« Last Edit: February 03, 2016, 04:15:29 AM by ziggyh »
ZiggyH

2007 Revolution LE
C9