Watching the "ignition light" on the MG-which per my understanding is both PART of the field excitation circuit and also tells whether or not the alternator is outputting current-is always a bit interesting. When you turn the key to the "on" position the light should illuminate. On my car, and on most others I've been around, after starting the light will initially stay on and requires a "blip" up to 2-3K rpms for the field to excite and the light to go out. The only cars I've seen where the light goes out immediately are the ones where the fast idle is set really high and the car is started with full choke(my fast idle cams are set to have the engine at ~1300rpms on full choke with the engine cold, although that will jump up to ~2500 on a warm engine provided that I manipulate the knob such that I'm only using fast idle and not enrichment). In any case, though, once the light is out it will generally only start to flicker on if the engine dips below ~500rpms-a speed that it's REALLY unhappy running.
At the same time, I often raise the idle to over 1K in the winter since with the extra draw from the heater blower motor, the headlights will dim noticeably below ~900rpms. I also run into a problem when I'm using the lights+blower+turn signals(and maybe wipers too) where the old thermal flasher won't actually flash at idle-I'm guessing the voltage to the turn signals is low enough that the bulbs aren't drawing enough current to activate the thermal flasher. I think that's evidence that I'm definitely on the threshold of what the alternator can supply, especially considering that even raising the idle a bit or blipping the gas will both brighten up the headlights and allow the signals to flash.
A Lucas 16ACR alternator is rated for 32A max, and presumably it's probably maxing at ~15A at idle. It's not too difficult to get there with a set of sealed beam halogens, especially when you start adding in tail lights and dash lights(never mind stuff like the blower and/or wipers). It's also no surprised that even a radio driving two speakers(I don't have anything in my car other than some unused speakers) can have idle issues. ~1975 and on used electric cooling fans in lieu of an engine driven one, and I consider them an overall good thing but I'd hate to think about adding them on to everything else at idle especially given that they're only run one speed and are also most likely to come on at idle. On popular upgrade is to fit an AC Delco alternator that was used on several Saturn models and has a peak output of ~110A. Of course, that also also requires another often overlooked upgrade in that you're now potentially(although not likely) shoving that much current through wiring meant for an alternator with 1/3 the peak capacity. If nothing else, though, it at least gives you enough current to keep everything happy on a cold, dark, rainy night with the radio on(although I'm usually not too happy in the car under those conditions
) .
At the same time, I often raise the idle to over 1K in the winter since with the extra draw from the heater blower motor, the headlights will dim noticeably below ~900rpms. I also run into a problem when I'm using the lights+blower+turn signals(and maybe wipers too) where the old thermal flasher won't actually flash at idle-I'm guessing the voltage to the turn signals is low enough that the bulbs aren't drawing enough current to activate the thermal flasher. I think that's evidence that I'm definitely on the threshold of what the alternator can supply, especially considering that even raising the idle a bit or blipping the gas will both brighten up the headlights and allow the signals to flash.
A Lucas 16ACR alternator is rated for 32A max, and presumably it's probably maxing at ~15A at idle. It's not too difficult to get there with a set of sealed beam halogens, especially when you start adding in tail lights and dash lights(never mind stuff like the blower and/or wipers). It's also no surprised that even a radio driving two speakers(I don't have anything in my car other than some unused speakers) can have idle issues. ~1975 and on used electric cooling fans in lieu of an engine driven one, and I consider them an overall good thing but I'd hate to think about adding them on to everything else at idle especially given that they're only run one speed and are also most likely to come on at idle. On popular upgrade is to fit an AC Delco alternator that was used on several Saturn models and has a peak output of ~110A. Of course, that also also requires another often overlooked upgrade in that you're now potentially(although not likely) shoving that much current through wiring meant for an alternator with 1/3 the peak capacity. If nothing else, though, it at least gives you enough current to keep everything happy on a cold, dark, rainy night with the radio on(although I'm usually not too happy in the car under those conditions
