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dshogman · 05-26-2008, 12:19 PM

I recently had 2 more lights installed on the underside of the overhead cabinet right in front of the cabinet holding the tank monitor, Hydro Hot switch, Onan control,thermostat etc. Going into that cabinet from the front side, there were two wires hanging down from the ceiling, red and black, both taped off. Installer found that they were 12v DC (at the time). So he used these for the dimmer switch for the new lights. At that point, the lights worked fine. A few days later when I turned them, nothing, nada, zilch. Checked fuses - all OK. And then the next day, they worked fine, bright. Now, two days later, I tried them again and there was first a dim pinpoint light in the middle of the light fixture, nothing else. Tried again, and the whole lense is lit very dimly. Everything else works fine in the electrical department.
OK, so what were the two wires that we thought was continuous 12v DC? Anyone have an idea?
Thanks.

dshogman · 05-26-2008, 12:19 PM

I recently had 2 more lights installed on the underside of the overhead cabinet right in front of the cabinet holding the tank monitor, Hydro Hot switch, Onan control,thermostat etc. Going into that cabinet from the front side, there were two wires hanging down from the ceiling, red and black, both taped off. Installer found that they were 12v DC (at the time). So he used these for the dimmer switch for the new lights. At that point, the lights worked fine. A few days later when I turned them, nothing, nada, zilch. Checked fuses - all OK. And then the next day, they worked fine, bright. Now, two days later, I tried them again and there was first a dim pinpoint light in the middle of the light fixture, nothing else. Tried again, and the whole lense is lit very dimly. Everything else works fine in the electrical department.
OK, so what were the two wires that we thought was continuous 12v DC? Anyone have an idea?
Thanks.

VAGABONDMAN · 05-26-2008, 04:09 PM

Could they be from the solar panels?

dshogman · 06-03-2008, 03:57 PM

OK, the lights now work - from a different 12v source. Turns out that when the tech tested those 2 wires coming from the ceiling, he just used a probe, and it lit up, so he assumed it was 12 volts.
Today another tech check the 2 wires with a voltmeter, and, lo and behold, 18+ volts.

So, new question for all the smart ones out there: what two wires come down into that compartment (see first post) and carry 18+ volts? Any thoughts......

EngineerMike · 06-03-2008, 04:09 PM

That's the 12 volt overtime circuit (time & a half).

Dave & Colleen · 06-03-2008, 04:34 PM

Dave
?????????That 18vdc on a system with only 12vdc. I have had several digital multi-meters that when the 9vcd battery starts to get low it gives false readings. However, all the functions appear to be working on the tester. Even on 120vac to read as high as 150vac.I now always carry a spare battery and discard them every 3mos. Check it with another battery or someone else's meter or even an analog one.
Dave

Mike & Mike · 06-03-2008, 05:25 PM

David,

I still think "solar panel" is the right answer. I just Googled "solar panel output voltage" and the first hit says 17.8 volts. I just looked in a solar handbook I've got and it says that the voltage can go as high as 20 volts. So, your 18 volts is in line with what's expected.

Finally, to put it more in perspective, here's a short excerpt from RVers Guide to Solar Battery Charging by Noel and Barbara Kirkby:

"A solar panel is attached to a battery in a parallel connection: positive poles to positive pole and negative to negative. As electrons from both the panel and the battery attempt to travel around the circuit, the high panel voltage (16 volts) overcomes the resistance of the battery voltage (12 volts). Thus, the electrons move toward the battery and recharge takes place ..."

I believe that if you read the voltage output of a car battery charger (or the charger on your inverter) you'd find that it's more than 12 volts also.

Cheers!

Mike Gamble · 07-12-2008, 10:56 AM

WE too have a 2005 40MDTS, and I discovered the two wires the same way you did. I waited until dark to discover that they are in fact the solar panel outputs. Do you have a solar panel charge status board under the sink in the bathroom? If the solar panels are connected, the little red light should be on during the daytime hours.

Renipladlo · 07-12-2008, 01:28 PM

David,
Is this the driver's side front cabinet up front? If not please be more specific with your description of its location, because I have the 2007 40 MDTS and I don't have a clue where you are talking about, and I read your post twice. I believe I found the #10 Solar Panel leads coming down into my battery compartment (PS-Rear of wheel), but I have not located the leads for the 10W panel, which I need to locate so I can disconnect them. The panel is fried.
Charging - The alternator puts out around 13.8-14.5 VDC to charge the batteries when it is being turned. It must (as previously stated) overcome the battery's 12VDC internal voltage. Electricity takes the path of least resistance; this is true for AC and DC current. Higher always flows to lower, in the utility industry we call it "loop flow", and there is a long and drawn out explanation for it, but the above will suffice.

Ted III · 07-12-2008, 03:00 PM

Dave, the meters we use do not need a battery to read an external voltage. I don't quite understand the purpose of the battery? The source gives you the voltage and the reading. If we are reading resistance then the battery becomes neccasary.

dgerstel · 07-12-2008, 06:15 PM

Monty,

In June I replied to your question about solar.

"WRV used 2 #10 wires, one for the 10 watt panel and one for the 100 watt panel. The one for the 100 watt panel was fused and the one for the 10 watt went directly to the large bolt (buss) in the battery compartment. I added a fuse to that wire for safety, that gage wire with a direct battery connection could cause big problems if it was shorted."

The #10 wire you see in the battery compartment is, most probably, for the small panel. The wire for the 100 watt panel is pre-wired from just inside the fridge roof vent and runs to the inside rear 12 volt fuse panel.

dshogman · 07-13-2008, 05:54 AM

Re: Mike Gamble's post above - agree with you that the two wires are from the solar panels. We did a similar check as you did. I guess the question is still there - what are they for?
("..cabinet holding the tank monitor, Hydro Hot switch, Onan control,thermostat etc..." on the 40 MD is overhead just to the left of the door, for whoever couldn't figure out the location.)
Thanks to all.

Mike Gamble · 07-13-2008, 06:09 AM

Our dealer (Holiday Motor Homes) was able to find the leads to the battery charging controller under the bathroom sink. I'm not sure how to identify them, but can take a look at what they hooked them to?

Renipladlo · 07-13-2008, 08:25 AM

Dale, Thank you.
Now it's just a matter of looking in there and figuring out (like you) where to put the fuse, etc.
It's not convenient having the coach one place, and me and the tools in another.