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Old 04-29-2013, 12:03 PM   #1
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12 volt problem

I have a 2007 32' southwind motorhome. If my main power switches are off and then I turn on the house power, my lights start out dim and then after 15 or 20 seconds (usually) they will get bright. While they are dim my voltage meter drops to around 8 volts, but when they get bright the meter is back around 12 volts or above. My batteries were down but I charged them up, and it is still the same. Any suggestions?

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Old 04-29-2013, 12:09 PM   #2
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Is this while plugged to shore power, or on battery only? And which battery are we talking about - house or chassis or both?

The superficial indication is that there is a major power draw for 15-20 seconds, pulling the battery voltage way down. Then whatever is doing it shuts off and the battery voltage bounces back. Typically something that might have that much power draw will be a heater or some sort, or a fairly large motor, but I can't think of what you might have like that. Is there an inverter in the coach?

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Old 04-29-2013, 12:10 PM   #3
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Sounds like you have some sort of high current load intermittently pulling on your batteries when you switch on. Water pump on? Do you have a power step that is not working properly/jammed? Something plugged into a 12V outlet that draws current and then goes over-current and switches off? Just guessing...

I know my LP detector is the first thing that starts chirping when I switch on but it never has drawn enough current to dim the lights/drop the voltage on the batteries.
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Old 04-29-2013, 12:15 PM   #4
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Sounds like a bad / dirty connection somewhere, and as the connection heats up from the draw it gets a little better.
With a multi meter check for a voltage drop between the battey post and the cable clamp.Or clean and tighten all connections on the batteries and check ground wires.
If all connections are good , and the batteries are original to the coach , it is time to take them out and have them load tested.
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Old 04-29-2013, 12:34 PM   #5
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What voltmeter? More importantly where is the measurement being taken?
You need a hand held one and start at the center of the battery posts for reference. Then move your negative lead to the frame somewhere it is shiny and clean. Then move the positive lead to a place where the wire is connected to something nearby. Once you establish the voltages are holding there you can move on but until you are chasing ghosts.

Often taking the terminals off and cleaning them along with the ground connections will solve may weird problems.

If it passes those tests you need to identify if it is the voltage going low at the light fixture or is the ground return failing. Easy to test but you need a long wire from the chassis ground or negative lead of the battery. Or use an 110 volt extension cord plugged in and just insert the ground lead of the voltmeter into the ground socket. Grounds should be common. Just don't plug into the 110 lead.

Now measure both sides of the bulb when it is dim. If you get close to battery voltage of 12 volts or more on the hot side and the bulb is dim your ground is sick. If low voltage then you need to work your way back towards the battery connections.
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Old 04-29-2013, 01:20 PM   #6
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It is not plugged in to shore power and it is only the house battery.
There is not an inverter either. It seems like the only thing that comes on is the LP detecter, but I will check that out.The batteries are 2 years old and they are 2 - 6 volts tied together. It has a digital volt meter on the display with all of the level indicators but I also check the voltage at the batteries and they read close to the same. All of the lights are dim at first.
I will check all of the connections that I can find starting with the ground cable, and then go through the checking sequence and see what I can find.
Thanks for all of the help.
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Old 04-29-2013, 06:16 PM   #7
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Several things could be energizing upon start-up. Refrig controls, A/C sensors, LP sensors & isolation solenoids, TV antenna amp, DC TV instant on, radios, leveling system sensors, steps and a whole lot more. Need to look at... not sure its a real problem for a voltmeter, maybe more a pain in the butt. JM2...
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Old 04-29-2013, 06:25 PM   #8
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Welcome to irv2.
Maybe this will help and do not forget battery grounds to chassis frame and clean terminals on batteries themselves.
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Old 04-29-2013, 06:41 PM   #9
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Originally Posted by 007";1549836]Welcome to irv2.
this will help[/URL] and do not forget battery grounds to chassis frame and clean terminals on batteries themselves.
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Old 04-29-2013, 06:54 PM   #10
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Could it be the relay contacts are lazy or a little burnt, not making good initial contact??
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Old 04-29-2013, 07:43 PM   #11
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On my other motor home, my fluorescent lights would not "fire up" because they were getting old. There was a small delay before they would "ignite." My new motorhome has quartz (or LEDs) and do not have this problem. Yes, a bad ground can also cause the problem or other parasitic drain but how old are your fluorescent tubes?
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Old 04-30-2013, 12:44 AM   #12
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batteries or supply problem

This is simple...there is a lack of current capacity someplace coupled with a seems to be high current condition.

Can be a pain, but not difficult.

First remember this..."divide and concur"..(spelling?)

You have possibly many issues that work together to make a strange problem or a single one in a common place.

DO not worry first about something drawing heavy load, focus on the dropping voltage, work until you find where the drop is, then fix it, simple.

Electronics 101 is simple...ALWAYS check the power supply.

Second, repeat all processes while making tests, so if you turn on certian devices in a certian order, repeat that each and every time so you have consistant results, change only to determine if the order is the problem.

Lastly, you need a "repeatable repair", can you undo what you did to have the problem return.

Now all that being stated, check the voltage at the battery, on the posts, and repeat for EACH battery.

Just because the battery measures 12.6 volts does not mean it is good, only that it has a charge.

If it stays at 12.6 volts when you perform your testing then the voltage drop is elsewhere, if it drops at the battery then the battery may be toast.

Next check voltage drop ACROSS connections, measure voltage from each post to ground, a bad ground will be seen as a changing voltage when testing.

Do not "shotgun" it, try to avoid wiggling wires, pulling and twisting things or cleaning battery terminals.

Best to "sneak up" on the problem, if you can find a bad connection via measuring the voltage drop, then clean or repair the connection and the voltage drop is gone, and the system works as required you can be fairly sure you got it.

Check from each post to the first connection, ground to negative post, the binding post or first connection on the red wire to the positive post.

Terminals can get acid inside and be good looking on the outside, measure first, clean later.

Now that the "power supply" or battery is tested, now divide system, locate the main power distribution panel, now determine the power feeds, consider these the same as the battery posts, repeat above testing.

If voltage is stable here issue towards load, if voltage drops, issue towards battery.

This will get you started, search for "power problems" and "troubleshooting" and you will find many more tips.
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Old 05-01-2013, 06:12 AM   #13
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Thanks for all of the help. I have found that 1 of my 6 volt batteries was bad and that my ground wire connection wasn't good. I am going through all of the connections and cleaning them, but it seems that has fixed my problem. One of my florecent lights doesn't seem to work correctly, so I might replace it with a new LED. Thanks again.

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