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Randall, RVIA Certification
Category: RV
Satisfied Customers: 10974
Experience:  RVDA/RVIA Master Certified Technician with many years experience.
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Classic: 12 volt question..converter when the shore line is plugged in

Customer Question

12 volt question with 2009 Aliner Classic. I just purchased this unit used. The l2 volt lights and appliances work through the converter when the shore line is plugged in. They also work when connected to the tow vehicle. They do not work with the camper auxiliary battery. The battery is new and fully charged. I have 12volt at the 20 amp fuse where the battery lead comes into the converter but no power on any of the 15 amp fuses to the appliances. Thinking it was the notorious Centurion 2000 I replaced it with an aftermarket upgrade. Same problem. All ground connections to the chassis have been cleaned and reconnected. Where is the problem?
Submitted: 5 years ago.
Category: RV
Expert:  Randall replied 5 years ago.
Hi: Thank you for coming to Just Answer with your question. My name is XXXXX XXXXX perhaps I can assist you with this issue.

Check the shortstop breaker on the positive feed from the battery. By code it has to be within 18" of the battery. Go HERE to see what they look like. Either it is bad, tripped if it is a resettable version, or the terminals are corroded. Some are hard to see and even need a small cover to be removed to see them. Some are out in the weather and more apt to have this issue. I suspect this is the source of this problem. Please get back to me if this doesn't resolve this for you. R.J.
Customer: replied 5 years ago.
Randall, This unit has a 20 amp fuse in the shortstop breaker. It looks and tested good and there is no apparant corrosion. Also, I do have 12 volt at the 20 amp fuse where the battery feeds into the converter.
Expert:  Randall replied 5 years ago.
Hook up the shore cord and take a reading at the battery to see if the circuit is complete from the converter. You should read about 13.7 VDC there. If so then the next thing is to see if the converter is the problem. Some have an internal switch that allows the switching back and forth from shore power to battery power and back. When it gets "stuck" in on mode you won't have any battery power when the shore cord is unplugged. Let me know what you find. R.J.
Customer: replied 5 years ago.
Last thing last evening I blew the fuse in my multi-tester. I am going to run to town and get a new one. It will take me about 1 hour to get back with you.
Sorry for the delay,
Be right back,
Expert:  Randall replied 5 years ago.
Not a problem, Jim............I will be here all day and evening as well until about 10 p.m. Eastern. R.J.
Customer: replied 5 years ago.
Disclaimer: I have a lay understanding of electricity and multi-meters so I am going to give you all the info I have. This is a pocket meter with a needle and not a digital read-out. I have it calibrated according to the manual but it can still be a little off.....The meter is set to DC V 50.

With the shore line plugged in and the battery wires connected to the battery I get about 12.5 at the battery. With the shore line plugged in and the battery wires disconnected I get about 13.5 on the wires that connect to the battery. On the top of the battery with the wires disconnected I get about 12.5.

I also have another deep cycle battery in another trailer. I pulled it cleaned up the terminals and got the same readings as with the first battery.
Expert:  Randall replied 5 years ago.
Sounds like you have the meter set correctly. The 13.5 VDC reading is about right. I am not following the "battery wires connected to the battery" as to what wires those are. And when they are "disconnected" where are you reading that 13.5 VDC reading? The battery reading about 12.5 disconnected from the circuits sounds about right. Fully charged it would be about 12.8 VDC. Please clarify the above for me. R.J.
Customer: replied 5 years ago.
Thank you for your patience. I have confidence that we are close to a solution.

First I read the meter with everything hooked up. The shore line was connected. At the battery the white ground wires (one short wire to chassis and one that goes back toward the converter) were connected to the negative terminal. The black wire (that goes back toward the converter) was connected to the positive terminal on the battery. I got about 12.5 DCV.

Next, I disconnected all wires at the battery and just read the volts on those wires. With the red lead from my meter touching the black wire that goes toward the converter and with the black wire from the meter touching either of the white wires at the battery I got about 13.5 DCV.

Then I tested the auxiliary camper battery when it was disconnected from everything. I got 12.5 DCV.

I am a crafter and do business at Irish music festivals. I use a deep cycle battery and inverter to power my credit card machine when 120 is not available. I got the deep cycle battery that I use with my business and ran through everything again. Same results.
Expert:  Randall replied 5 years ago.
Either this converter is putting out this voltage at a very low level and it will take the battery much longer to charge OR the battery has some shorted cells and is not absorbing the charge. If you leave it on for about an hour hooked up and plugged into shore power see if it increases. That still doesn't resolve the issue of no power when you unplug. That would be a converter issue IF the battery is good. Have it tested. What is the make and model of the Power Center in this coach? That would help me to know how to direct you. R.J.
Customer: replied 5 years ago.
The camper came with a Centurion 2000 converter. I went online and read as much about this converter as I could find. I read that this unit does not have any built in protection in the event the battery wires are reversed. Secondly, I read that my problem is common with this converter. Third, I read that this converter is generally problematic.

I purchased and installed WFCO 8735P. The change was straight forward. The new unit fit the old hole with very little modificaiton. The wiring was easy to understand. I marked all my wires with tape to make sure I did not get anything mixed up. When I turned it on nothing blew and everything worked. The problem is that I did not fix my problem with the 12v.

I really want to fix this problem today if possible. Right now I am going to take the batteries back to town to have them tested at my regular mechanic.

Randall, thank you for your continued help. I may need your advice again before this is done. No matter what happens I will tell you now that I am going to click the "accept answer" at the end of our conversation and give you the best rating because you are doing a good job helping me.

Be back in an hour or two.
Expert:  Randall replied 5 years ago.
Customer: replied 5 years ago.
My mechanic tested the battery. It is good and fully charged.
Expert:  Randall replied 5 years ago.
Then the converter must have an issue IF it reads good voltage when you don't have the battery in the circuit and drops to nothing when you hook up the battery. WFCO isn't the best unit around and it may be dropping out on load..........rare, but it can happen and it is always the stuff you don't expect with new parts. This would take testing that I don't have information on. It should be under warranty. R.J.
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Expert:  Randall replied 5 years ago.
Thank you for the nice bonus............much appreciated! Please tell your friends about our service here at Just Answer. Most of the time we can get you an immediate answer and save you a bunch of $$$ as well. Please come back again if you have another issue "down the road" and be safe! R.J.