It's the battery cable?

A few months my voltage regulator was ineffective (replaced it) and the ensuing drainage and load on the battery rendered the battery basically useless. Can you say 90 available cranking amps? Anyways, replaced the battery.

Now 3 months into the present, the car seems to be having starting issues again. Considering i just changed the battery and the voltage regulator, it has to be either the battery cables, the alternator, or perhaps there's a slow leak. I took a meter and measured 0 milliamps when in series with the positive terminal and it's associate cable.

So i decided to take some voltage measurements...

Car off...
Battery: 12.2V
Alternator: 12.2V (pos and neg terms)

Car On(idle)...
Battery: 12.6V
Alternator: 13.8V

Car On(engine sped up)...
Battery: 12.6V
Alternator: Forgot to measure

Do you think it could be the cables? I need to check the alternator voltage w/ the engine at speed, but even 13.8 V should be 'OK'. Surely the voltage should be the same at the battery.

What do you guys think?

Sounds like serious alternator issues.

Load test the battery, but it sounds like an open or shorted or weak diode in the alternator bridge and/or a bad regulator. You can get a free alternator test at a Sears shop or buy a minitester (I have a Sun) for maybe $20 or so at AutoZone. The minitester may have three or four LED's that light up in a pattern that tells you if you have low voltage, high voltage, open or shorted diodes (essentially a high ac component in the rectified dc output).

OTOH, if you have an oscilloscope, go for it and look at the alternator voltage waveform. It should be a series of lumps, all the lumps on the same side (+) of the abscissa. Any lumps below indicate a shorted diode (replace the bridge or most likely the alternator if you can't get a bridge)...missing lumps indicate an open diode.

You can't really measure ohm resistance in these battery cables. The issue is voltage drop which can only be measured with current running in the cables.

You must use a high impedance voltmeter, generally a digital voltmeter or multimeter (DVOM). Set it on the 2volt range and put one probe at the battery and other probe at the other end of the same battery cable. You can ground the secondary ignition wire to ensure the engine won't start (and protect the ignition system!) and then crank the engine and observe the highest voltage reading. Some meters, Fluke or my Sears, have a min/max setting that will keep the highest reading...if you have one it's easier than watching the meter all the time. The deal here is that E=IR, or the product of the cable resistance and the current flowing through it will give a voltage (drop) that you're measuring. It should not be more than 500millivolts or 1/2 volt or so. Anything over 1.5 volts is grounds for immediate replacement of the cable or some serious connector work (maybe the cable ends have bad connections).

OTOH, it could just be a worn starter. It happens.

Could you elaborate on your 'starting issues' ?

If you are having trouble getting the starter to turn, use one line of a jumper-wire-set to connect from the -ve battery-post directly to the starter body (the head of the starter-bolt is a good spot), and see if this helps. That's what helped me isolate a bad grounding-wire to the engine.

Noel

I'm sorry, i forgot to include the concern.

The car has starting issues. When it's hot outside, sometimes the car just wont start. The starter doesn't turn at all. All accessories work. If it's cold outside, the car will start, OR, if you jump start the car.

When I got the new battery, the car started up without a problem even when it was hot. But it sounds like the starter is spinning slower and slower, and just the other day when it was hot, the car didn't start. But it did when i jumped it.

measure the resistance (in ohms)in the wires not voltage to isolate problem.

Thanks. I will. The voltage measurements were done to see if the alternator and/or voltage regulator could be a problem.

When you jump-start the car, do you attach the -ve jump-start cable to the engine-body or to the battery-terminal ?

If you attach it to the battery terminal and it starts up fine, dont bother doing what I suggested in my earlier post (attaching a jumper-cable directly from the post to the starter-body), since that means the engine-grounding cable is fine.

If you attach the -ve jumper-cable to the engine and it starts, do what I suggested and see if it makes a difference.

Noel

Yeah, I jumped it via the negative battery cable.

I'm not really sure what sort of resistance values i should be looking for. I know i'm not getting very accurate readouts. Obviously a large resistance isn't good, but I'd expect such a big thick cable to have a large resistance.

Actually, you should be looking at 0 resistance. Think of that thick wire as being hundreds of thin-wires in parallel.

That being said, 1 or 2 ohms could show up if your meter-probes dont make good contact with ground or wire-terminals.

Noel