12 volt electrical

[gocamping14]

had a 12v electrical drain in camper, seem to have found the issue, but in the process of elimination found another puzzling issue. have a WFCO elec. box. **the camper was not hooked up to shore power during the experiment below, only on the battery, fully charged** camper in barely 3 years old, with minimal miles.

have 8, 12v, 15amp fuses. I pulled all out in troubleshooting the previous problem. only 3 of the 8 red lights camp on indicating a blown fuse or break in the circuit. should have all 8 red light come on??

fuse #1 (lights) tested 11.43v again no fuse in
fuse #4 (furnace) tested .93v
fuse #5 (radio) tested 12.34v
fuse #7 (kitchen) tested .05v

the other 4 terminals tested 0 volts.

why was there volt present in some terminals and not all ?

any thoughts appreciated.............ss

[MrWizard]

The only time a control board ( fridge furnace water heater ) , does not use power is when the battery is disconnected
The on/off switches for these devices do not control input power are not in the input power fused line, they connect to the board to supply a yes/no ..on/off signal
So there is always some power draw unless disconnected
It is usually in milliamps..but several devices over days or weeks ..yes it can drain the batteries.. this parasitic drain is always there when batteries are connected

[handye9]

SoundGuy wrote:

handye9 wrote:
There is a control board in both the refridgerator and furnace. These boards draw some power even when the unit is turned off.

:h That would be news to me ... can you substantiate that with a link to documentation indicating this is so? Not challenging you, just interested, as I'm quite careful about controlling parasitic draw in our trailer, even added kill switches to the radio and TV antenna system, also the climate control heater in the fridge. Nothing runs in our trailer unless I know about it, including the fridge and furnace, so if I'm mistaken I'd like to know about it. :?

I can't say if you're mistaken, or if I am. I was repeating something I had seen in other threads.

Your question got my curiousity going, and I spent most of this morning, trying to find something in writing. So far, what I found by searching the web for RV parasitic draws, was more forum threads, on various RV sites, discussing this same topic. Some of those threads mentioned inverters, televisions (12 volt), radios, CO2 detectors, circuit boards on newer water heaters, air conditioners, funnaces, refridgerators, and the newer fuse panels, with the LED (the little light that comes on when a fuse is blown) indicators.

I even called Dometic and talked to two different reps. One said they do have a parasitic draw, and the other said they don't.

Where it actually says yes, no, or a specific quantity, I can't find it.

Maybe, one of our electrical wizzards will know.

[SoundGuy]

handye9 wrote:
There is a control board in both the refridgerator and furnace. These boards draw some power even when the unit is turned off.

:h That would be news to me ... can you substantiate that with a link to documentation indicating this is so? Not challenging you, just interested, as I'm quite careful about controlling parasitic draw in our trailer, even added kill switches to the radio and TV antenna system, also the climate control heater in the fridge. Nothing runs in our trailer unless I know about it, including the fridge and furnace, so if I'm mistaken I'd like to know about it. :?

[time2roll]

Bobbo wrote:
No, that is not what he is measuring. He is measuring ACROSS the fuse connector.

Ah ha!

Need amp reading instead of voltage. Then poke around to get the amps to zero.

Kitchen is probably the propane detector... no switch to turn off and for good reason that it could be left disabled.

[schlep1967]

Try this. Put your black lead on the ground bar in the panel (accessed by removing the panel cover). Touch your red lead to the supply side of the fuse holders. Doing this you will see there is 12 volts present at all of the fuse holders on one side and 0 volts on the other side. What you were measuring before was the voltage actually being used at the time by that circuit. It is just a matter of what you are measuring across that has you confused.

[Bobbo]

smkettner wrote:

gocamping14 wrote:

fuse #1 (lights) tested 11.43v again no fuse in
fuse #4 (furnace) tested .93v
fuse #5 (radio) tested 12.34v
fuse #7 (kitchen) tested .05v

the other 4 terminals tested 0 volts.

why was there volt present in some terminals and not all ?

any thoughts appreciated.............ss

Just to clarify... ALL fuses are pulled and you are measuring voltage at the fuse connector, yes?

Battery voltage on one side and these listed voltages on the other side, right?

No, that is not what he is measuring. He is measuring ACROSS the fuse connector. That is the voltage on the battery side, using the other side as the ground, through whatever 12v devices are turned on and pulling current. The fuses with nothing on and pulling current he said read 0 volts.

[time2roll]

gocamping14 wrote:

fuse #1 (lights) tested 11.43v again no fuse in
fuse #4 (furnace) tested .93v
fuse #5 (radio) tested 12.34v
fuse #7 (kitchen) tested .05v

the other 4 terminals tested 0 volts.

why was there volt present in some terminals and not all ?

any thoughts appreciated.............ss

Just to clarify... ALL fuses are pulled and you are measuring voltage at the fuse connector, yes?

Battery voltage on one side and these listed voltages on the other side, right?

I also would expect all to be zero with fuse removed. Something appears to be back feeding these circuits. Furnace might have something to do with the thermostat. Radio could be an antenna booster? Lights, no idea. Kitchen, fan? more lights? no idea.

Try grounding them for a moment in case there is a circuit board with a capacitor.

Time to pull the power center from the cabinet and take a look behind.

[MrWizard]

Moved from technology

[handye9]

There are some parasitic drains, in most RV's.

There is a control board in both the refridgerator and furnace. These boards draw some power even when the unit is turned off.

There is continuous power going to the CO2 detector.

There is continuous power going to the radio.

Only way to kill these circuits is disconnect the battery.

Maybe, the three circuits indicating a power loss, were the three that I mentioned above.

If your problem is draining the battery while not connected to shore power, that is normal. You need to install a disconnect switch or actually disconnect the battery itself.

[Bobbo]

Those lights only come on if there is a load on that circuit pulling current. If there is no load, there is no red light.

Turn on all your 12v devices and all the red lights should come on. Think of the 12v stuff that is turned off as opening the switch to turn off the light. With the switch off, there is no voltage, no current, no light.

[ScottG]

The reading you get depends on the type of load the fused device is presenting. In your case, the radio's memory is a heavier load (relatively) than the furnace in it's standby mode so the voltage is higher. The loads of those devices are creating a connection to ground and completing the circuit for your meter.
The path to ground provided by some of the smaller loads may not be big enough to provide a ground for the LED's to light.
So what your seeing is reasonable.