[unruhjonny]

It just occurred to me that I could ask this here (DUH!);

How can I check if my alternator on my 2009 Cobalt might be going?

Background:
My 2009 Cobalt SS has been a fantastic car, with only one hiccup requiring an engine change;
I take blame for flashing a too aggressive tune and causing mishap from driving it a bit too hard.
I have absolutely no plans of replacing this car, because quite frankly, I don't feel as though anyone offers anything that comes close to this car for visibility, comfort, horsepower, fuel economy (if I keep my foot off the "go" pedal), and reliability.
... Well there's one that's close, it's a 2018+ Honda Civic Type-R, but other than the stats, I'm not a fan.
Plus I have a spare engine to rebuild for it

I have owned my Cobalt from new (ten years next month), and although I have occasionally put off some maintenance with no real excuse, typically I try to be ahead of the ball with what needs to be done, or what might be coming up.

I have noticed for a little while now that when my cooling fan turns on, it momentarily dims my headlights;
I am wondering if my alternator might be going, or if there is something else I should look at - I have a spare low-mile alternator, but I'd like to be a good student of my former boss, and properly diagnose if there is an issue or where the issue is rather than just throw parts at it.

I do not have a TechII, or any other high end diagnostic equipment;

If it is my alternator, how might I do a proper load test?

If it might not be my alternator, what might anyone suggest I do to chase this down?

Thanks in advance to anyone who's willing to offer advice.

[PunchT37]

What does the volt meter read when the lights and fans are on? Do the lights dim just momentarily when the fans start then return to normal?

[unruhjonny]

it happens so quick, that I haven't observed any reading fluctuation;
it goes back to normal, but it has become quite noticeable, and I don't recall it doing this years ago.

[PunchT37]

You can bring the alt somewhere and have it load tested. You can check for amp draw on those fan motors and compare to spec. Prolly not a big deal. But I`m playing keyboard mechanic.

[jerry455]

How old is the battery, if it is older you may want to test it. The turbo Ecotec's were an amazing motor. It is impressive what power can be had from those. GM printed a good book on building the Ecotec engine. I think ZZPerformance did a lot with those also.

[dataway]

I'd lean towards the blower motor or the battery being the problem. A good battery should take up the load instantly on a blower motor in good condition, probably before you'd see anything. If the blower motor is going it could be drawing way more amps than it should on start up.

Simplest thing first. Test the battery.
Blower motor ... if you can get to the harness might be the next easiest thing to check.
Might be able to check the blower motor draw at the fuse .. but that would require a VOM with pretty high DC amp settings.

Or if the alternator is easy to remove .... take it in and have it checked after the battery.

[ta6point6]

Take it to any local parts store like Autozone or Advance Auto. They can test the whole system in the car. If none are close and have a volt meter turn on lights to bright, AC (is best)on to high or heater to high. Test at battery positive and negative, should be getting 14 volts back from alternator.

[unruhjonny]

thanks for the tips;
I am incline to want to test it in place, because of the work involved to get it out from it's hiding place... I seem to recall that hte tensioner is a royal pita to get at, and then the bolts that hold the alternator actually hit the rad before being able to come out (or some malarky like that);
Yes, these are fun little motors...