Charging 101


#1

can a over charging alternator destroy a distributor.


#2

Depends on the distributor I suppose, an old school distributor does nothing but transmit spark, so no problem there, model specific would be helpful.


#3

Did someone tell you overcharging would destroy a distributor ?


#4

Yes, but by the time the electrical system voltage would be high enough to do that I would imagine many/most/all other electrical items would be fried as well.


#5

You’d fry the coil(s) first.

Boiled down to it’s simplest, the alternator generates an AC voltage that’s changed by the regulator to DC in a process called “rectifying” and regulated and filtered. That voltage is fed to a winding of fine wire around an iron “core” of the coil. The current flow creates an electrical field. When the current flow in the winding is turned off, which in an old style distributor-based system is done by opening the “points”, the magnetic field collapses and induces into the iron core around which it’s wound a “spike” of voltage. That spike is then sent by the distributor to the proper spark plug.

In short, 12VDC goes through the coil’s winding and the distributor’s “points”, which turn the coil’s circuit on & off. The coil induces a high-voltage “spike” of perhaps 50,000 volts and sends it through the distributor’s rotor and distributor contacts, where it’s sent to the proper sparkplug. It then jumps the gap in the sparkplug, grounding onto the engine’s block, and back to the battery.

First to go would probably be the points, the rotor, the distributor cap, and the “condenser”, a capacitor in the distributor assembly included to prevent a charge from building on the “points” and prevent transfer of material from one point to the other as they transfer the voltage spike to the spark plug wire. But they’re all routine maintenance items anyway. Next to fry would probably be the coil windings.

I know this might be confusing, but I’ve tried to simplify it as much as I could. Hope it helps.
Is there a problem you’re trying to diagnose? If so, what’s the year, make, model, mileage, and engine of the vehicle?


#6

I would think you would toast the ignition module or whatever primary side control resides in the distributor to operate the coil. Points would burn up with normal battery voltage, I imagine an ignition control module would tolerate up to 16+ volts without much issue. I’ve seen 22 volts coming out of the alternator, but at that voltage I imagine lots of other electrical failures on the car.


#7

Yes, among other things. It would depend on how much overcharging was actually occurring.


#8

You’re probably right for most systems. I was just thinking the problem through and making some guesses.

Which brings up the question for the OP: is there a problem associated with the question or was it simply hypothetical?


#9

The battery limits the voltage to less than 16 volts in normal operation. If the alternator is putting out too much current I can see that voltage raising by a few volts or so, although the battery would be damaged.

Of course if the battery is defective, then the voltage can reach a much higher level, and if it is open or disconnected you can get to 40 volts.

But all auto electronic assemblies/components are tested (or should be) for that voltage, just for that reason, in case someone disconnects the battery, or the cable goes bad.