Skip to main content ↑ ↓
Topic: No 12v power on shore power/generator (Read 606 times) previous topic - next topic

No 12v power on shore power/generator

I recently bought a 1995 U-300 SE that is in beautiful condition.  We were aware that the house batteries are junk and need to be replaced.  But, when I got it home and plugged it in I still have no or very little 12v power for interior lights.  There is a Heart power inverter/charger in the large passthrough storage bay but I can't find the 12v converter anywhere?  Even if the batteries are shot, the 12v converter should still be running all 12v house systems off shore power or generator right?  I also have a Xantrex controller above the door that is showing <10v in the coach and a volt/ammeter that shows 0.00 for both.

Re: No 12v power on shore power/generator

Reply #1 –
Welcome to the Forum and congrats on scoring your U300SE.  A bit of terminology clarification will help the discussion.

A "converter" receives AC power and converts it to DC power that is used to charge a battery, or to directly power DC devices.

A "inverter" receives DC power from a battery and inverts it to AC power.

A "inverter/charger" performs dual functions.  It can take DC and convert it to AC.  It can take AC and output DC to either charge a battery, or (in some cases) to directly power a DC device.

SO, the question is, what do you have on your coach?

If the Heart device is a inverter/charger, then it NOT likely that you also have a converter.

OTOH, if the Heart device is only a inverter, then you probably DO also have a converter.

Can you take a photo of the Heart device and post it.  Would help with long range troubleshooting.

The spec sheet linked below, from our ForeForum WiKi, lists the standard equipment for 1995 U300.  However, older coaches are often modified/updated from factory original specs.

https://wiki.foreforums.com/_media/through_the_years:specs:1995-u300-specifications.pdf

Our exceptional ForeForum Library has an extensive collection of electrical schematics.  One of the two linked below should cover the 110V relay system in your coach (most likely the second one).  Your 1995 U300, although still a Unihome design, was built during a transition year, and shares many of the same system components with the later Unicoach models.

https://www.foreforums.com/index.php?media/item/a-2700-07-110v-elect-relay-system-u280-u300.3267/

https://www.foreforums.com/index.php?media/item/a-2700-07-1995-u295-110v-elect-relay-system-wiring.5207/
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: No 12v power on shore power/generator

Reply #2 –
If its the original Heart Freedom 25, then this should be the manual: The selected media item is not currently available. This is the version after Heart was sold to Xantrex, since you mention your interior panel says Xantrex.

Just to say it out loud, if that is the original, its 30 years old you really should begin to consider upgrading it as its on borrowed time (IMO) ... its also a modified sine wave output which is not "great" these days.
2000 / 36' / U320 / WTFE
WildEBeest / "Striving to put right what once went wrong"

Re: No 12v power on shore power/generator

Reply #3 –
The remote panel for the inverter should have a switch to turn on charge, to charge the batteries. If that is turned on and still not charging it is probably no good.
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: No 12v power on shore power/generator

Reply #4 –
Thanks all. Links to photos below.
The inverter/charger is a Heart Interface Freedom 25.
When the coach is plugged into an extension cord at the house (20 amp), the Xantrex panel initially shows the following:
AC In - Battery State Full - DC Volts 10.0 (Red light) - DC Amps <10 (Green Light) - Incoming AC Breaker Amps set to 20.
 
If I turn the power switch off on the inverter for about 10 sec. and turn it back on, it starts humming like its working (having some off-grid living experience I am familiar with the buzz).  While it's buzzing, the control panel shows DC Volts 13.0-DC Amps 25 and everything that is 12v powered in the coach works great. 

Go out an hour later and it's back to the first scenario and I reset the Inverter again.

https://www.dropbox.com/scl/fi/okax00xj4vc2hdyeif5il/IMG_7897.HEIC?rlkey=ord71ae7qlgcxtlgrjsahj4kk&st=nimc1hmi&dl=0
https://www.dropbox.com/scl/fi/8j1rbts8bw8umio5ofwmy/IMG_7898.HEIC?rlkey=75fddk9chi17s1rb00bd6nvuq&st=7pyj685t&dl=0
https://www.dropbox.com/scl/fi/ln9b8sihqwhsaf7glgg1c/IMG_7900.HEIC?rlkey=ha0ngb0h7l0o0yloyrk7l3d69&st=tx2usvee&dl=0
https://www.dropbox.com/scl/fi/3ajci5u8v5rztd4xd6foy/IMG_7901.HEIC?rlkey=5rzdfkg9ugtj1vuj41ogrbiwp&st=a5vceo2m&dl=0
https://www.dropbox.com/scl/fi/25t6l49oyhvoliqb6bwyo/IMG_7902.HEIC?rlkey=d8pdywcg5yi5bockqaykmhddt&st=kufklj6o&dl=0
https://www.dropbox.com/scl/fi/rc2ysj2wwaia79cnl92dq/IMG_7903.HEIC?rlkey=y4mthmk8bfc5c7bif2ycvekpv&st=4yrfzy39&dl=0

steve: edited/Attached images for quick viewing

Re: No 12v power on shore power/generator

Reply #5 –
The batteries indicating 10 volts and the charger topping off and shutting down quickly indicates the bank is probably bad. I would begin with having the batteries tested outside the rig. Charge and load test. It is possibly time also to upgrade the inverter/charger.
Dennis Haynes
Bohemia NY
2008 Nimbus 342 SE Carlyle
Build #6475
Motorcade #19148

Re: No 12v power on shore power/generator

Reply #6 –
You can try the whats in the manual
Quote
To successfully charge an over-discharged battery, you must remove as much DC load as possible and set Power Sharing to the lowest setting.
Which basically is trying to trickle charge the batteries back to a nominal level.  It sounds like the unit is simply turning itself off as a protection.  Chances are the batteries are not recoverable but maybe the slow bring-up may give you some time.
2000 / 36' / U320 / WTFE
WildEBeest / "Striving to put right what once went wrong"

Re: No 12v power on shore power/generator

Reply #7 –
Turn the power share down to 5 if it will go that low.
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: No 12v power on shore power/generator

Reply #8 –
Agree.  That 5 amp setting of 120 VAC will charge the batteries at over 40 amps @ 14 VAC. Plenty!
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020