Charging circuit, 1964 Barracuda
Still doing some planning for rebuilding my engine compartment wiring harness. It seems that the weak spot in the wiring is taking the full current through the bulkhead fitting to the ammeter. I plan on using headlight relays to cut down on some of the current. The wiring “killer” appears to be when the alternator tries to charge the battery. Has anyone attempted to bypass the ammeter and wired the alternator directly to the battery? Any advice or opinion would be greatly appreciated. Alright, some opinions may not be appreciated.
Thanks, Ken
A couple of years of the early cars had big huge feedthrough busses for the ammeter circuit. Figure out if yours is or isn't before getting excited.
Start by reading the MAD article which explains the how and what of the ammeter circuit problem. It is not just the bulkhead connector. It is that plus undersized wiring, problems that can occur at the ammeter terminals, and inside the ammeter itself
http://www.madelectrical.com/electricaltech/amp-gauges.shtml
You can run a fused/ breaker protected larger wire direct from the alternator stud to the battery, and Crackedback one here sells one made up nicely.
BUT you also need to repair the bulkhead terminals because they will still be used (in parallel, effectively) to feed power into the passenger compartment.
Headlight relays are not a bad idea, not only because of the ammeter circuit weaknesses, but because factory headlight wiring is too small, anyhow
The other issue that goes on is OVER charging (overvoltage) because of voltage drop in the harness. This is caused in part by drop in the ammeter circuit, BUT ALSO is caused by the bulkhead connector terminal outfeeding the ignition "run" voltage (which powers the VR), as well as drop in the ignition switch connector and the switch itself. This can be "fixed" by using a Bosch style relay, triggered by the key "ignition run" voltage, to then feed the loads under the hood, the VR and the ignition system.
What happens is, the drop in the harness causes the VR to "think" the battery is low, because the VR is seeing this voltage drop. So it ramps up to maintain it's power terminal at nominal 14V. Now the battery runs high because of the difference between the VR (with the drop) and the battery which is higher.
You can check for this by turning the key to "run" with the engine stopped. Stick a probe of your mulltimeter into the top of the battery POS post, and stick the other probe on the VR IGN terminal. Whatever that reads is how much "over" the battery will see. Anything that reads more than about .3V (3/10 of a volte) consider looking it over.
