Tip & How-To about Volkswagen Beetle
There is confusion when a car won't start because a starter can be
shorting/binding and drawing too much current or have a discontinuity
and not draw enough, or a battery can have too little current or have a
discontinuity preventing it from providing enough. But it is possible
to tell with just a simple voltmeter or even a test light.
First you check battery terminal for being clean and greased, belts tight, enough battery water, engine not binding, etc.
Then test the battery with the engine off, and expect 12.5 volts. If less, then charge it up or replace it.
Then when you try to crank the starter, it should drop to about 10 volts.
If it does nothing and stay above 12, then it could be the ignition switch, neutral/clutch safety switch. See if the current gets to the starter solenoid. If it is getting current or it clicks, the starter solenoid is not closing the current to the starter field windings. That could be because the solenoid is bad, or the field could be burned out and open. You could try to shunt the solenoid, but it is probably easiest to just get a new starter.
If the voltage drops down to 9 or less, then either the battery does not have enough reserve, or the starter is shorting/binding and drawing too much current. The way to tell is what happens when you stop trying to crank. If the battery really is bad, it will not come back up to 12 volts, at least not right away. But if it was the starter, then it should come back to 12 when you stop drawing on it. (But don't try to crank it too long.)
Finally, lets assume you do get it started, either with a new battery, charging the old one, replacing the starter, fixing switch, etc. Then when you rev the engine, it has to put out over 13.5, so that it can charge the battery. Over 14.5 would be bad because it would overheat the battery and dry it out. But with less then 13.5, even a new battery will not last more than a couple of days. But at idle speeds expect only 12.5 or so. If you don't have a voltmeter, you can see the headlight brighten slightly when reving up.
Posted by Kirk... on
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