looking for electrical "leak"

[kevinkatz]

my battery in my 1965 caravel goes flat if left connected. naturally the old trailer has had electrical modifications and still has a rats nest of wires in the original box under the goucho. i took out the univolt and put in a 4 stage boondocker convertor.

i am an old hotrod guy. when we wanted to check for a drain on the battery we took a terminal off and put a light or voltmeter between the removed wire and its terminal. if the light lit up, or there was current on the voltmeter, it meant that something was drawing current.

when i did this on my trailer there was a voltage equal to the voltage across the battery making me think that something was drawing current. however nothing is on at all. the lights are all off. i have no fridge. the hot water heater is electric only. i switched off the breakers, took out the fuses, disconnected the electric brake wire, disconnected the boondocker convertor, disconnected the remote wireless brake controller and still there was current running.

so i wanted to check if there is continuity. this is where i am shaky on knowledge. put multimeter on ohms. goes to Lo. when connected together goes to zero. so i put it on the positive and negative battery wires with the battery disconnected. it goes to some other number like 6.4 or something but it isnt stable. what does that mean?

any other ideas would really help from this group of great intellect, knowledge and wisdom. thanks in advance.

[Lumatic]

There are a few electronic upgrades that have a parasitic draw. I know radios for sure. I am not so sure of appliance that have a circuit board such as a fridge.

[uncle_bob]

Hi

Ok, so basic troubleshooting. (Except it's anything but basic ...)

If there is voltage on the wire, an ohms check will be wrong. You can only read ohms with a multimeter if you check for volts first. Zero volts means you can go ahead and check for ohms.

Current checks are the easy way to look for stray loads. One lead of the multimeter goes on the + post of the battery. Everything is turned off and disconnected. Only one other wire goes to the second lead on the multimeter. If there is a circuit drawing current on that wire, you will get a reading. The current comes out of the + post on the battery, goes through the meter, goes through the load, goes to the shell of the trailer, and goes back through the big cable to the negative post on the battery. Any time you are doing current checks, be careful of burning out the meter. If you suspect a > 10A current (and your meter is rated to 10A) start with a light bulb.

Stray voltages are a different thing. In theory, with everything turned off and the battery disconnected, you should have no voltages (except on the + post of the battery). If you *do* get voltage readings, then something is still connected. It could be an "extra" battery buried somewhere. It could be the super capacitor on your sub-woffer. It could be a connection to your tow vehicle. There are (unfortunately) a lot of possible culprits.

Ohms checks are fine, but they are checking at low voltage. A load may or may not behave the same at 1V as it does at 12V. LED lights are one good example of this, there are lots of others. Bouncing ohms readings can mean a lot of things. Most often they mean you have an intermittent connection. A slowly rising ohms reading means you have a capacitor at the other end of the wire.

The "usual suspects" for leakage currents are things like lightbulbs in odd places, smoke alarms, carbon monoxide monitors, "damp chasers" (dehumidifier heaters), and on and on. The "divide up and run down" approach is the way to find them. Never assume there is only one single leaker. Also check your ground to make sure it's still attached. It's really embarrassing to go through a bunch of checks and then notice you pulled the negative off the battery. Don't ask how I know this

Bob

[Belegedhel]

Try disconnecting your battery, unplugging from shore power and the tow vehicle, and then set your meter to ohms. Turn everything off (or better yet, unplug/disconnect everything). Now, put one probe on the lug for each outgoing circuit at the fuse panel, and the other to ground. If you have a leaking circuit, you should see a relatively low resistance to ground. You can then isolate that circuit and try to find out exaclty where it is leaking. If you find no leaks, then start reconnecting appliances, and rechecking the circuits. Common culprits might be circuit boards in the refridgerator, and thermostats, but there could be others.

good luck!