Engine stumbles at idle under electrical load?

[bmwman91]

Any ideas on what this might be due to?  For instance, when I turn on my headlights the idle stumbles a little, and when I come off-throttle it will stumble a tad too with the headlights on.  My last car did this as well.

Is the alternator going out, or just not producing enough power or what?  Thanks.

[1991318is]

sounds like alternator to me
Take it to a shop and they can test those for free, atleast all the shops round my house will. It only takes a minute w/ no work besides connecting the tester to the battery terminals.

[kowalski]

yeah it sounds like your alternator. i'll get on the write up for the 150 amp gm alternator when i get home from europe (3 weeks) as i leave tomorrow and i still need to write a calculus final, and pack. so i have no time... so if you can wait, i'd recomend it. You could also just go buy a 2 wire gm self exciting alternator, the wiring is straight forward as its the same as ours, just make sure to buy the 2 wire plug with the alt. and then you will need a welder handy, and 4 pieces of flat bar about 4 inches long each that you can cut to size. and weld 2 of them to the top bracket, you will also need a large washer depending on the thickness to bring out the pully to the right distance, and you will also need to get a new belt. lets see what else... oh remove the rubber washer type pieces that are pre-existing in the mount holes, and if you can make spacers to fill them for the bolt so it doesn't have any play.

[jfdublyu]

mine does the same thing, but i'm procrastinating b/c I want to upgrade somewhow

[bmwman91]

Well, I suppose I will wait for the 150A writeup.  What is the difference between it and ours/the 2-wire self-exciting one?  And how much do they cost usually?