12V power issue

First thing I noticed is you told nothing about your batteries.

Are they GC-2 pairs (Two six volt golf car batteries in series to make 12 volts)
or 12 volt MARINE/deep cycle, and if the latter Group 24, 27,29 31 or something else? It matters.. Just like flashlight batteries, You would not expect an AAAA (Yes that's 4 A's) to last as long as say a "D" cell..

So we do need to know.. Also have you checked, if they are Flooded wet cells are the plates covered with fluid (Acid/water mix) or are the tops of the plates exposed (Not good) if flooded fill with DISTILLED water to about 1/4" BELOW the bottom of the filler tube more or less is ok but below the bottom, not to the bottom..

And tell us more about your batteries.

OH, Very good choice on converter.

0.25V drop could simply be from the resistance of the wires themselves, particularly if there's a goodly amount of current flowing. At, say, 30A, a 0.25V drop implies about 8 milliohms of resistance, which according to a chart I found online is what you'd have with about 21 feet of 6 AWG wire.

You did find and fix a serious problem.

OK, so thanks for the clarification between "neutral" and "negative". Understood the concept, not the phrasing :)

I redid all the suspect wiring over the weekend. Cut all the wires back beyond the corrosion and reconnected with split bolts, which I taped (plastic - rubber - plastic) separately and secured so they don't bounce around. Now it seems everything is working great. I'm still showing a small voltage drop (~0.25v) and I suspect I have a ground connection somewhere that is corroded or suspect. After running everything in the unit I could for a few hours, the wires were still stone cold, so I think that problem is solved.

Now on to figuring out why the step doesn't work now - thinking it may be related to my last little bit of voltage drop. But - I'll play with it and put a new post out if I can't figure it out.

Would there be any issues with removing the step entirely and working on it on my workbench instead of laying on the ground under the motorhome?

Two wires a positive and a "neutral" from the battery is actually a positive and a connection to frame ground. There are no "neutrals" in the 12V system, only positive and ground. I believe you've found your issue. You were probably trying to charge the frame.

OK, so I traced all the wires out and made sure all the supply wires were good and all the grounds were good. While doing the grounds and moving wires around, I found a very hot wire bundle. I killed the power and unwrapped it, it was two bundles of neutrals and one bundle of hots, all wrapped together, and melted. Looks like that may be my issue. Looks like a factory job, or at least a professional one, so not sure why it is. I'll fix the wires, wrap them individually, and try it out. Will update in a few days...

I'm using two 6v batteries, new last year. I maintain them as I do the golf carts I maintain (several). Thus far, they are testing ok, but to make sure I'll put another set in to verify. It is grounded to the frame with about two feet of wire, and I did check that to make sure it was a good connection, etc.

I unplugged the converter and disconnected the positive on the first battery. There are three red wires terminating into the 12V power panel. I disconnected all three of those and toned them out. One goes to the converter. The other two seem to go to a solenoid by the chassis battery. Not sure if that is the battery disconnect or the emergency start solenoid. There are two connections to the positive on the battery. One of those also tones out to the same place under the hood, but I have not yet located the other. I get a very quiet tone near the battery disconnect switch. I'll go crawl around underneath it and see if I can see where it goes.

It seems odd that two wires would terminate in the same place, no?

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You probably have bad batteries if they haven't been charged in awhile. The deep cycle batteries should never be allowed to drop below the 12.0VDC level.

You probably have boiled out the fluids and the battery has gone bad on you now...

Using a meter across the battery terminals should read 12.6-7VDC when fully charged and if it reads below 10VDC then it is basically a dead battery... My shorted out batteries usually only read 5VDC when measured.

The PD9100 and 9200 series smart mode chargers will take care of your batteries for you when you finally get a good battery to maintain...

There may be problems with your wiring or switching as well for the system not working and this is why you need to measure across the battery terminals to see what the DC Voltage level reads there...

I always look at the battery to read where the NEGATIVE TERMINAL is located...(Says NEG or SYMBOL '-').. Then I make sure this battery cable goes directly to frame ground close to the battery... If this has ever been wired wrong then you will have some blown fuses in the the path to the converter/charger unit.

Connecting the multimeter to the battery terminals is also good for making sure it is getting a charge voltage. Like said above it should read 12.6-7VDC with no shore power on and is fully charged. If you connect to shore power and the converter/charger comes on line then this DC Voltage should jump up to 13.6VDC or higher depending what charge mode it is going into. Mine will read as high as 14.4VDC when in boost charge mode. If you don't see this increase of DC voltage then something is not connected from the battery terminals to the DC output terminals of the converter/charger unit. Or perhaps the converter/charger unit is not turned on from the 120VAC side...

Roy Ken

OK, I'll work on that tonight. I did check the 120v coming in and the 12v from the converter to the panel. It seems to go from there to two other places, I assume one is the battery.

I did notice that when the batteries were not installed (I took them out for the winter and kept them indoors and charged), nothing worked, even with the converter going. I thought that was odd, but suspect from what I have read that it is normal. Didn't think to include that on my original post...

Start by checking your 120VAC incoming power and keep tracing thru the converter out toward the battery. You likely have a blown fuse, a loose or corroded connection, or a broken wire.