67 mustang using more power than it's charging
 

bought a '67 289 a month ago and have been doing some work here and there on it. previous owner said to disconnect the battery when not using it so I looked into it a little online. ordered+installed a 100 amp alternator (self regulating) and disconnected the regulator. checked the ignition switch (it appears to be cutting off power properly) and re-did his ****ty wiring and installed a cut off to the electronic fuel pump and wired all that to the ignition's accessory switch. And rewired the system so he doesn't have the radio + switches going straight off the battery.

there's a modern radio, 3 speakers in the back, all white interior lights were replaced with blue, hood turn lights, no dome light.... i just don't understand how so much power could be drawing that a 100 amp isn't enough. I'm not the greatest mechanic, so does it make sense to you guys? I'm pretty lost at this point.

It should be said that when I got it, there were tons of cut wires plugged into twist caps, and still have some wires hanging that I don't know what they belong to - under the hood.

Also I connected the one positive terminal to the positive starter relay with an 8g wire

you'll need a multimeter for this set it to DC voltage in the 20V scale if its not autoscale.


1) Measure battery voltage what is it?
2) measure battery voltage with the engine running what is it?




engine off should read 11ish and should read13.5+ running
If you aren't getting in the 13s with the engine running there is a alternator or perhaps battery issue


so lets say it read 10.5 with the engine off and 13.8v running
This would be an indication that something is causing the battery to drain but the alternator is working however whatever is causing the battery to drain is pulling a lot of current and kills it over a short period of time when its sitting.


3) remove the ground cable from the battery and set the multi meter to Amps you'll have to switch the dial to 10A range and likley switch the test leads to 10A unfused and common. conenct one end of the meter to the battery post and the other end to the - wire so the meter completes the circuit is the current draw 500mAh? 1A 3A? I would be concerned about anything over 150mAh that would accommodate for a clock on a cd player...nothing else should be running. if its over 1A then yeah there is a light stuck on or an amp thats still powered up causing the battery to drain down quickly when the cars not running.

Check what Gun Jam said first. Then think, did you ever run the new alternator with out it being connected to the battery? I suppose this is a single wire alternator. If so, you may have blown a diode. Diodes usually blow shorted. If this is the case it will try to make the alternator into a motor and suck power from the battery when not running. If the battery reads low when the car is off and you disconnect the alternator, and then the battery reads OK , the alternator need a new diode block.

Sorry for the late reply, I had to charge the battery and work came up.

Gun Jam - I wrote down various measurements throughout the day while driving around yesterday to this morning:

12.08 - Initial Battery Charge
14.43 - Vehicle Running
12.23 - Vehicle Off
12.11 - Vehicle off, and After Waiting 5 Minutes
12.68 - Vehicle Running, w/ Radio + Car Charger On
12.12 - Vehicle off, After waiting 15 Minutes
12.24 - Vehicle On w/ Headlights, Radio, Car Charger
12.48 - Vehicle On w/o Headlights, Radio, Car Charger

Then I disconnected the battery before I went to bed. Woke up to 11.94. Drove to work, disconnected the battery, and it was still 11.94. Got off work and went to Autozone and had them replace the battery (their tester said it only had 1v) and with the vehicle on it was only at 12.25.

I unhooked the battery while the vehicle was running (I was told if the alternator is the problem, doing this would cause the vehicle to shut off) and it kept running, however my radio turned off.

Yes bop11, the alternator is a "Powermaster Alternator 100 Amp One-Wire V-Belt Pulley." It's funny you should mention diode's, someone else had suggested that to me. They said there's a diode under the dash that goes out that could be the cause. Is that the one, or could there be any truth to this?

I don't remember any diodes under the dash. The Alternator has either 6 or 9 diodes in it. The main six convert the three phase AC output of the alternator to DC. The output of the alternator is controlled by a internal regulator (one wire alternator) which controls the voltage in the rotating coil part of the alternator. The more voltage the more amps output. Some alternators have a set of three diodes to feed the regulator, some feed the regulator from the alternator output internally. The battery acts as a big capacitor to damp out spikes in the output. The spikes can be grater than 400 Volts and un-damped can blow the diodes and other electrical parts in the vehicle but mainly kills the diodes in the alternator. Diodes normally die shorted and since they block the flow backwards from the battery, when blown can cause the battery to discharge through the alternator wiring. This is the reason that you should never disconnect the battery when the engine is running.
Disconnects can also come from a bad ground or a lose wire or bad cable. I had a V-12 jag that kept blowing diodes because both the alternator and the engine mount were aluminum and they corroded to a point where the ground connection through the alternator case was intermittent.
There are many posts on the internet on how to test for bad diodes.

Engine running, voltage at the battery should never go below 13.5, no matter what
is turned on. The radio alone, pulling it from 14.4 to 12.9 is not good.

The 'Spikes" come from relays, when the field collapses at the coil. The magnetic field
around the coil collapses, which "tries" to keep the current flowing in the same direction
as it was when it was powered. This can cause very high peak reverse voltages so you
use what is called a "freewheeling diode" to provide a path for that spike, or short-circuits
the coil and lets the coil's internal resistance and the diodes voltage drop consume the
energy. A car battery is not a capacitor, it cannot spike voltage. Energy in a capacitor is
stored in an electric field, when the field collapses, is when you get the voltage pike. A battery
stores its potential energy in a chemical form, thus discharging it is slower because of
the latency associated with chemical storage. A battery is a source of energy for a circuit,
whereas capacitor is a passive element, which draws energy from the circuit, to store and
release it. You'd be lucky to even get a 20V spike at a car battery, and only a short will
cause it. Older car instrument clusters, they have voltage gauges that go to 19 VDC. If
you see that needle climb to 19, and it stays there, your battery is going to explode...
My 2003 silverado has an analog voltage meter to 19. There is NO WAY you're getting
a 400 volt spike generated BY the car battery.

Diodes in an alternator are for a totally different reason. The rectifier diodes convert the
magnetic AC field to DC voltage the car can use. The diodes in the rectifier serve as a
one-way check valve so that the polarity stays consistent while charging the battery.
And, since the diodes will only allow electrical current to flow in one direction, energy
feedback that may travel as far as the diodes, won't get into the alternator itself. The
alternator will then be isolated from any energy returns which can damage the alternator.

Blown diodes are still protecting the circuit, but no current flow in either direction.
Shorted diodes do not, as shorted ones allow current flow in both directions, hence
the fluctuation and pikes. You ever see people's car lights pulsing? That's what
happens when even one diode shorts. It's due to the severe voltage fluctuations.

A blown (open) diode reduces output voltage, and changes the circuit from a full to
half wavelength.

AMPs determines the charge rate of the battery, not the voltage. Voltage determines
the push of useful current through the battery internal resistance. This is why charge
voltage has to be higher than the rating of the battery. 12V is pushing from the battery,
so pushing 12V back into the battery is equalized, and does not charge the battery.

Honestly I can't find any schematics displaying diodes on it. I have a physical Haynes manual but it doesn't have any in it either.

So, this is weird. When I got home the battery was at 12.34, an hour or two later it was 12.40-ish. now its 12.50.

looks like the alternator is good.
perhaps the old battery had an internal short Ive heard of this before where the battery pretty much discharges it self.


OR


there is a parasitic voltage draw on the battery that is significant. This is where you can use the current or amps to measure how much draw there is on the battery when the car is off and the key out. Disconnect the - battery cable and set the volt meter to amps then touch one lead to the cable and the other to the battery post. all current must flow through the meter and the meter will tell you how much current is being used.