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01-20-2025, 02:00 PM
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#1
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Member
Join Date: Aug 2014
Posts: 45
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1999 Freightliner XC charging house batteries?
Are the house batteries supposed to be charged by the engine driven alternator while on the road? I'm seeing maybe 12.5 volts at the batteries with the engine running. Doesn't seem like enough.
Thanks!
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01-20-2025, 02:07 PM
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#2
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Senior Member
Join Date: Oct 2014
Posts: 8,845
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Yes, the alternator should be charging both chassis and house battery banks.
__________________
Brett Wolfe
Ex: 2003 Alpine 38FDDS. Ex: 1997 Safari Sahara. Ex: 1993 Foretravel U240
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01-20-2025, 02:18 PM
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#3
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Member
Join Date: Aug 2014
Posts: 45
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Thanks Brett for the reply. I don't have my schematics with me...is the charging circuit protected with a fuse? Alternator is new and charges the chassis batteries nicely
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01-20-2025, 02:40 PM
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#4
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Senior Member
Join Date: Apr 2011
Location: Powell River, B.C.
Posts: 34,185
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Freightliner doesn't supply the wiring and solenoids involved in charging the house batteries, from the alternator ; your coach builder did .
What make and model is your coach ?
__________________
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
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01-20-2025, 02:45 PM
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#5
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Senior Member
Join Date: Apr 2011
Location: Powell River, B.C.
Posts: 34,185
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Some systems want to see the chassis batteries fully charged , from the alternator , before switching to charging both battery banks .
How long did you run the engine before testing the output to the coach battery bank ?
__________________
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
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01-20-2025, 03:11 PM
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#6
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Member
Join Date: Aug 2014
Posts: 45
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1999 Winnebago Chieftain 36 diesel
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01-20-2025, 03:12 PM
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#7
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Member
Join Date: Aug 2014
Posts: 45
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About 15min. Dash gage shows about 15V but not sure of accuracy of gage.
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01-20-2025, 03:29 PM
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#8
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Senior Member
Join Date: Oct 2010
Posts: 1,541
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does your coach have relay isolators, or diode isolators? If its diodes, you're dropping.75V on the way to the batteries. Hopefully your alternator has a sense wire that will bump the output voltage to compensate (if the wire is hooked up)
__________________
'99 Beaver Monterey 30', Cat 3126/300
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01-20-2025, 03:42 PM
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#9
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Senior Member
Join Date: Jul 2014
Posts: 37,096
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If your really seeing 15 volts, that means you have the wrong alternator or a missing sense wire.
That can burn out the diode type isolator, if equiped.
Post pictures of the battery control compartment.
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01-20-2025, 04:24 PM
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#10
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Senior Member
Newmar Owners Club Freightliner Owners Club
Join Date: Aug 2023
Posts: 334
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An alternator typically delivers around 14 volts DC. I have 2 vehicles w/alternator readouts on them and one is always at 13.9 and the other at 14.2. Years ago I had a 2-yr old battery die and traced it to a bad alternator delivering less than 10 volts; the new alternator now reads 14.0 volts (vs the previous 13.9).
15 volts however seems high. So not only does it appear the alternator may have failed to the high side, but a protection circuit between the alternator and battery has done it's job to protect your batteries from a dangerous overcharge. Whether it is a solenoid, relay, or fuse is dependent on your chassis.
Alternatively, has any work been performed recently w/the chassis batteries? If so, maybe things weren't hooked back up correctly. Also ensure the cables on the alternator are bolted on tight or they're not damaged in any way.
Lastly, how old are your batteries? Old batteries cannot hold a charge as well as new ones. So if they're old, the 12.5 volts -- the low end of a charged battery -- may be telling you it's time to replace them. Fully charged batteries should read above 13.2 volts. Cold weather only exacerbates a battery's weakness ... Don't know what the temperature is where you're at, but I've given more battery boosts to stranded drivers more times in the Winter than Summer. I remember because helping folks in the bitter cold and knee-deep snow s**ks more!
Good luck
__________________
'22 Newmar Dutch Star (Freightliner)
'20 Jeep Wrangler JL
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01-20-2025, 08:19 PM
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#11
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Member
Join Date: Aug 2014
Posts: 45
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I'm on the road and using a cheap VOM. I will buy a new digital one tomorrow so I can see what is really going on here.
Thanks for all the help!
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01-20-2025, 08:19 PM
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#12
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Senior Member
Join Date: Apr 2011
Location: Powell River, B.C.
Posts: 34,185
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Quote:
Originally Posted by Panheadguy
1999 Winnebago Chieftain 36 diesel
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A look at the wiring info on the Winnebago site may provide some answers about the way the house battery charging system works.
http://www.winnebago.com/Files/Files...ram/Wiring.htm
__________________
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
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01-24-2025, 03:11 PM
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#13
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Member
Join Date: Aug 2014
Posts: 45
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I looked. Info overload for me!
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01-25-2025, 07:39 AM
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#14
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Senior Member
Join Date: Jul 2017
Posts: 985
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If the battery's are truly charging at 15 volts you will have a heavy sulfur smell in the battery compartment. Dash gauges are close at best but not 100% accurate, cheap volt meter are about the same a decent quality is going to cost you but worth having or you can go into any automotive shop and usually they will test the system for free and test your batteries.
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