These may seem like stupid questions, but on the notion that "the stupidest questions are the ones that didn't get asked," here goes:

If I were to add a large electrical power load to my slant van, like a big honkin' stereo or an inverter running tools or appliances or something, does my engine have to work harder to produce the additional electricity through the alternator, or am I simply tapping into power that's being produced (up to the limits of the alternator) anyway because the alternator is belted to my crank pulley and spinning whenever my engine is running?

Does the alternator itself work any harder under such a circumstance--ie, is its lifespan shortened by increased electrical load?

I hope I'm being somewhat clear. Thanks in advance for any helpful input.

The alternator requires more power to turn as its load increases.

The alternator only charges as much as is needed. That is, it is not creating much current when it is not called for, which is the 'job' of the volatge regulator. The voltage regulator senses how much load there is on the vehicle's electrical system, and 'tells' the alternator to increase or decrease output accordingly.

So, yes, if you were to add a large electrical load, the alternator would have to work harder, and consequently the engine must work a little harder to turn the alt.

-S/6

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The "Silver Bullet"
87 Ram D150

If you want to see that principle in action, do this: Idle the vehicle with the headlights and all the accessories "on". Temporarily disconnect a field wire from the back of the alternator or unplug the regulator and notice the increase in engine speed (small, but noticeable) when the load from the alternator is removed.

D/W

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If it ain't broke, fix it!