Back from the Grave

I have replaced the wiring harness in any old car that I have owned older than 1950. Invariably, when replacing the harnesses in my 1936, or 1931, there have been bare wires in the old harness. The 1931 had bx conduits, and I found bare wires on steel! Someone told me that after 1950 there was rubber under the cloth outer layer.

David,

I know that it is a cheesy comment, but I believe that engine compartment mousetraps were a PAMCC factory option.

Peter

Wiring terminology, and wiring issues in our Pierce Arrow cars [and other cars of the era]

For anyone and everyone reading this: a quick note on wiring and insulation: a crack or bare spot on a wire does not in anyway make the wire fail at conducting electricity, the wire is not bad. The function of insulation on wiring is to keep anything from touching the outside a wire to actually make contact with the electricity- conducting wire itself..

When a wire has something touch it’s conductor before the conductor reaches it’s intended destination, this causes the electricity to take a shorter route back to the source of the current: the battery.. This is the origin of the term ‘a short’.

A broken wire, a loose connection etc is NOT a ‘short’. A short is always dangerous, since the electricity is NOT going were it was intended, and often creates heat, fires, arcing or other damage.

However, I do not intend to imply that a wire with cracked insulation, loose connections or frayed insulation is ‘OK’ to ignore, or to leave as is.. Cracked insulation is an indication that the insulation is old, became rigid instead of remaining flexible, and vibration or flexing caused the hardened insulation to crack, and often crack and flake off in chunks.. But the wire is still ‘good’, that is; the wire is still conducting electricity.

Any wires found with hardened, cracking, or shedding insulation should either be replaced, or the bare conductor wrapped in electrical tape, shrink-tubing, or even have a piece of small rubber tubing slid over the conductor.

The ‘sneaky’ problem is the weak or loose connector at the end of the wire. Most wiring has the connector crimped on the end of the wire, providing not only an electrical connection, but a mechanical connection with a method of connecting the wire to the device it is supplying electricity to. The crimped connections eventually loosen when vibration and flexing of the copper wire eventually cause the pressure of the ‘crimp’ to become loose.

A loose connection will often ‘LOOK’ like a good connection: mechanically sound, and conducting electricity. But often the connection is NOT conducting current, and is only marginally holding the wire mechanically to the intended device. So a gently ‘wiggle’ of each wire and a close look at the wire at the crimp connection is needed to see if the connector’s crimp is still sound..

In critical locations, crimped on wire connectors should be soldered to the wire. Soldering makes for a near-perfect electrical connection, and a much more sound mechanical connection.

Our Pierce Arrow cars were wired with the ‘then’ standard methods: the wires behind the instrument panel often were not supported in the middle, between the two ends of the wire.. On wires only going a short-distance between devices, generally bracing or added support is not needed..

But often there are several wires that are long enough that the steady bouncing and vibration from the vehicle traveling down the road will constantly flex the wire, put strain on the connectors, and eventually cause connections to become loose, and eventually fail.

The cars with a current limiter mounted on the inside of the firewall, have a wire about 20″-24″ long between the current limiter and the ammeter or to the ignition switch on the steering column. This wire is often rarely supported in the middle, and it is often the cause of intermittent problems and eventually causes the car to not start or to have many electrical issues.

Greg Long

Thanks Craig. I’ll check with Arnold and David to see if they want another article.

Greg Long

Adding to Greg’s great comments I’ll add one more thing that is often overlooked on older vehicles. Many cars use the chassis and body for the ground instead of home run ground wires. When new this was fine but with age corrosion builds up where the metal to metal joints are on the frame, between the rivets, where the ground cable attaches to the frame, etc. Each little bit of corrosion adds to the resistance and causes dim lights, slow blinkers, horns that sound like a sick duck and and engine that barely turns over. Adding an additional ground direct to the starter can make a big difference in cranking speed. Sanding to bare metal where the cables attach is another big one. Just another thing to look for.

All electrical systems work great until you let the smoke out.

Once the smoke escapes it’s over.