Electrical wire.

[Karl]

G'day.
Looking for some info from the electrical wizes out there.

Recently I replaced the four wires that run along the drivers side rocker cover to the coil, temp sender, oil pressure switch and air conditioner compressor.
The air conditioner wire was cut back to the firewall by a previous owner but the other three wires I believe were original. They were hard to bend and not in good shape. The wire that went to the coil had the original terminal end and for all appearances was still ok however under the insulation could have individual wires broken or corrosion.

Since I replaces the wires the engine has seemed to be running better, this could be just me, or it could be because of some other matter that I have dealt with that I can't remember or maybe it is just mind over matter.

My question is would replacing 1.5 meters of wire from the firewall to the relevant item and I used what we call here in Australia as 4mm wire ( this is not 4mm thick but equivalent to your #12 wire, 3mm is equivalent to #14 wire).
The reason I use the heavier wire is the outside dia of the wire is more closely matched to the old wire diameter on the car. I believe today's wire has thinner insulation on it compared to the old wire which has thicker insulation on it, Could this improve the running of the engine?
The oil pressure and temp I am not worried about it is just the coil wire. Being that the voltage is lower than the 12v, if the wire is old will this reduce the current flow?

Many thanks,
Karl.

[kbuhagiar]

I would venture a guess that your repair most likely fixed an intermittent problem that you were not aware of. That original wire (especially the one to the coil) may have degraded to the point that only one or two of the strands were still intact. Your repair likely restored full current flow to the coil. So it's probably not your imagination.

I don't think the thicker wire gauge itself would make a difference, but all things being equal, if you are faced with a situation where you need to decide between using a smaller (thinner) wire or a larger (thicker) wire, always go with the larger one whenever practical. Of course, based on any given situation, YMMV.

In any case, congratulations!

[Rusty57]

The original wires for the ignition, oil pressure switch, and temperature sender were at the largest our 16 gauge. It would not surprise me if the switch and sender wires were only 18 gauge.

The AC wire could have been as large as 12 gauge if it was directly activating the clutch. If it was just activating a relay it would have been maybe 16 gauge.

Your replacement wire is more than adequate. As kbuhagiar noted, you probably were having some issues due to degradation of that smaller wire over time.

Auto manufacturing is obsessively driven by cost. My observation is that they really push the limits by always selecting the smallest wire possible they think can safely handle the load. The other advantage is that smaller wires are more flexible and easier to route.

You might not have noticed this. In a modern car all of the control systems are very low milliamp signals operating at 5 volts. You will see lots of 28 gauge wire in control circuits.