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Dead battery problems and a no start condition may result from your alternator not charging the battery. This is a very common car and truck concern. Most people will need a mechanic to sort this out, but there is one simple thing to try first.

Bonk the alternator with a hammer!

Why? (you ask!)

An alternator that has been around for some time, say one hundred thousand miles or more, can get sticking brushes. When the brushes stick in their holders, they may lose contact with the commutator rings. A sharp rap on the alternator case, (not hard enough to cause damage, but just enough to jar the parts), may get those brushes back in place.

If this intervention is successful, how can you tell? Well, if you have a voltmeter, have it reading system, (battery), voltage before you do the bonkin’. Engine running, but alternator not charging, voltage will probably be around 11.5v, maybe less if the battery is getting tired. When the alternator starts working this voltage should jump to 13+v to 14.7v, (depending on how depleted the battery is). You should also notice a distinct whining sound from the alternator as it works to charge the battery, possibly a drop in engine RPM and a brightening of the lights.

Interestingly, I just had this whole scenario play out on a 2001 Ford Escrort. I posted this article a few weeks ago, and on Tuesday, December 16th, 2008 I got a chance to review. The car came in with a not charging concern. I verified the condition, battery warning light on and system voltage, with the engine running was at about ten volts.  I then tapped the alternator and immediately the thing started charging. When I got the old unit out, I removed the regulator and brushes and one was worn down to where you could see the copper wire rubbed through the carbon. The contact ring on the armature had a corresponding groove cut into it. This examination proved that the procedure we are talking about is diagnostic and not a repair, though it might get you home.

Now for some more detail on the parts we are discussing. An alternator is a generator that produces alternating current, like household current. The alternating current is changed to DC (direct current) by passing it through a rectifier. Direct current is what the battery and the car’s electric system uses. The electricity is produced when wound wires are spun past a series of magnets. In order to get this electricity from the spinning rotor out to the car’s wires a method of contacting the spinning parts is used. This is done by the brushes I mentioned earlier. They are square carbon rods, about 3/16ths inch wide by an inch or so long. They sit, loosely, in square tubing holders that have springs in the end to push the brushes against the commutator. The brushes also have a wire each, that is connected to the rectifier and voltage regulator. Considering the environment they work in, these are amazingly reliable systems. Eventually, though, the brushes wear to the point that they can get sideways enough to stick in the holders. This is where the hammer comes in.  

This post is a rewrite of an answer I gave to a question on another site. The problem was that a number of components, all on the dash or instrument cluster, were inoperative or had their warning light on. The vehicle was a Ford Explorer. I got to writing and didn’t stop until I had strayed some. Might be helpful for some of you with electrical issues, though.

When a vehicle has numerous codes in different systems, a low voltage condition is often the cause because modules do not do well at voltages below, say, nine volts. A low voltage condition can happen when the alternator is failing, or a battery is depleted by a draw and upon starting, the voltage is low for a period. In this condition, the PCM and other modules are testing their circuits and finding a lot of things out of spec. That is when codes are set. This may be a time to write down all codes and save freeze-frame information, if available. Then clear codes and retest or drive. However, your description includes systems that are module controlled and very sensitive, (passive restraints, i.e. air bags, and ABS), and systems that are less sensitive to resistance issues, (like rear window defroster which is just a heating grid and very basic). The backup light is controlled by the TPS, transmission shift position sensor, which is part module and part plain old lighting. So, my advice is to look for a bad ground connection. When a system loses a ground, it will try to ground the current wherever it can, (ever heard of the ‘path of least resistance’?). Often this is through another component making that component function oddly. Ford puts ground connections at several places under the hood, behind the front kick panels, (those plastic trim panels outside of the front passenger feet areas, both left and right), and in the rear quarter panel inside the car, behind the trim. These grounds use green screws with 8mm or 10mm hex heads. They are obvious because they have a bare eyelet screwed right to the body metal. Another critical ground is the frame to body strap. Since the body is rubber mounted to the frame, a dedicated ground is provided. In the old days, like twenty years ago, a corroded strap was not an unusual problem. Odd things would occur, for instance a customer would complain of flickering lights and, by the way the u-joint is making noise. What would happen is, without a ground, the body electrical would seek a ground through the driveshaft and back to the engine and generator. This current would etch the u-joint bearing surface and cause it to fail. Weird, huh? But true. Test this by running a wire from the battery negative to the body.

Sorry, but since those are such different systems you describe, each could just be bad on its own.

One other thing, has your car been struck by lightning? Probably not, as it isn’t likely to run afterward.

That was my answer, for more electrical discussion go to the chassis electrical blog heading