Tuesday, September 4, 2012

Taming electrical beasties, part 1

The first step in fixing the battery drain is to build a schematic. To do that, I first had to open things up and take a peek.

I wish I had taken a picture of the battery compartment when I first got the van, just to document what I had to contend with. The battery terminals had stripped wire wrapped around them, with several different hot leads leading away. The insulation was a little bit of electrical tape on the lid of the battery box. So the first thing I did was put crimp-on connectors on all of these wires, so I could be sure that the connections were good, and put a proper insulator on the hot leads from the battery.

The next step was to wander around the van with an ohmmeter and a piece of paper, to try to get some idea. The previous owner had noticed the drain, and he'd placed a large switch next to the door post to disconnect a circuit he'd installed in the back. I don't think it addressed the issue, and it looked ugly. So my buddy Josh and I traced the circuit from the switch, and produced the following map:

I don't expect anyone to read that. It just highlights that the wiring was a mess. There are several electrical sins being committed:

  1. Several unrelated items are on the same circuit, all fed with a single 14AWG hot wire.
  2. There are several places in which the circuit "branches." When I was first doing residential electrical work, when we had a hot wire one place and needed to fan it out to several things, it was considered OK, but iffy, to install a "pigtail," a short loop of wire in one twist connector to bring hot to another twist connector right next to it. Taking a single hot line several different directions, in several different places along the same circuit, was never OK.
  3. There's an unfused light coming directly off the battery. It might be unlikely to short, but it's still a fire hazard.

To address the issues, I ran separate hot wires for the things I thought belonged together: the Propex heater has its own, the lights and 12V adapter share one, and the shower pump has its own. (The shower pump probably doesn't need an entire circuit of its own, but water and electricity make me nervous, so I wanted this on a pretty small fuse.) I also put in a new fuse block, to make measuring the current draw from each of the circuits easier. Here's what the aux battery box looks like now:

Of course, none of this actually got to the real problems. I'll talk about how the Prior Owner didn't have a monopoly on incompetence when I finish up with this spot of electrical rework.

No comments:

Post a Comment