Strange Battery/Alt problem

If you havent already done so, clean your battery terminals,ground connection, check the electrolyte levels, and check your belts.. Make sure all the infrastructure is working. (Belts with glaze, replace, etc)

Then try again. A lot of winter problems are caused by these problems.

If all else fails, you may have to replace the alternator, but take care of the basics first.

The light comes on because the battery voltage is too low. This is most likely an alternator issue but it can sometimes be a battery issue.

Your alternator was failing... it was producing lower voltage that it was supposed to.... at higher RPM it would work, but at lower RPM it would not.

Your alternator was completely dead and your battery somewhat discharged by that time as well.

This is pretty much normal, and indicates your alternator had started behaving by then.

It doesn't do a damn thing that you can't do yourself. But the problem you describe sure sounds like a failing alternator.

It's more likely the regulator board failing, but bad brushes can sometimes act this way too. It is ALSO possible for a bad engine ground to cause intermittent issues like this, so check that the engine ground strap is nice and firm and all the connections are good.

When you buy a new alternator and put it on, take the old one apart and look for cold solder joints on the regulator board and for damaged brushes.

It's most likely the alternator.

--scott

Also if your battery is older it might be a good idea in invest in a new one if/when you get the alternator.

Yes the battery tester is not much different than a DMM except the battery tester can do a load test on the battery to test its strength.

If your connections are clean & tight & belts good your alterator is the problem.

Thanks for the replys. I guess I'm still just wondering why it only seems to happen when the engine is cold and I don't believe it has come on again once it goes out and the engine is warm. Maybe the regulator isn't working when it's cold. It is interesting how on a couple of occasions revving the engine shut the light off temporarily until the car warmed up. The car also has 234K miles on it and this is the original alt that came with the vehicle.

You may have some soldier joints that pull apart when cold, then when they warm up, they expand and make better contact. Just a thought. Anyway, you are on the right track.

-Doc

I think you are describing either a loose or polished up fan belt. They will act exactly as you describe.

I test mine by taking a cold off engine and seeing if I can hand slip the alternator pulley. If I can, the belt either needs tightening or is polished and needs replacing. The alternator takes several HP to spin up under load and if you can hand slip it cold, for sure it will slip under use when cold.

Mike

With that high mileage I would suspect that your brushes are worn/ sticking. Probably R&R of the alt. and replacement of the brushes combined with a good cleaning would solve the problem. I have seen your exact symptoms on several old VWs/Porsches that were of "a certain age." Light would come on at low RPM especially when cold but when RPMs were increased they apparently made good enough contact to provide proper output (but probably not at full rated amperage)

I'm not sure how to properly advise you however - I am skeptical of the quality of a typical parts store "reman" but then again have heard that the newer post-10/12SI Delco alternators aren't particularly good straight off the assembly line, either. If you don't feel comfortable tearing into it yourself my personal preference would be to remove it and take it to a good auto electrical shop that does rebuilds in house and just tell them to make it right. You'll pay through the nose, but at least you will get a good rebuild.

I see that Mike has suggested checking the belt as well; that's also a good thing to check but you didn't mention any squeaking/squealing in your post. Usually but not always you will hear a noise if the belt is slipping. However if the belt is really old you may want to just go ahead and replace it before digging into the alternator.

good luck

Nate

I agree with snipped-for-privacy@hotmail.com that brushes are the most likely problem. The brushes conduct the exciting current from the voltage regulator the the coil on the rotor of the alternator. They wear over time and eventually get too short to reach the slip-rings. The combination of a high-mileage alternator, intermittent output and slowly worsening symptoms supports this scenario. The fact that your symptoms are presently temperature related does not eliminate this possibility.

Some alternators have replaceable brushes, for others you just need to replace the whole alternator. I once got home with failing brushes by shaping the braided bush wires so the they did not hang up on the brush holder. I replaced the brushes soon after (VW Rabbit).

How good an alternator you need depends on how long you plan to keep the car. I've never had any trouble with a parts-store alternator; it would most likely work better than your existing one does now.

It is a little dangerous to try to diagnose without doing any testing. All of us have had odd experiences with charging systems, I would suspect.

This is no time to start changing parts.. That gets expensive. Diagnose.

Look through the whole system and be sure before you fork out a lot of money.

I have never personally had an alternator which did not have replaceable brushes, but I bow to your experience.

I have had several batteries that tested good, but weren't. Alternators are usually fairly easy to test (but not always).

Work systematically. Be sure you understand the system, and buy replacement parts when you are pretty sure that is the problem.

A lot of rebuilt alternators are truly crap. If the OP has a local alternator/starter shop, I might recommend you go to them. They have more experience under their fingernails than most Autozone or similar counter salesmen.

This is very similar to what the alt in my dirt track Camaro does.

It's not the same alternator it's the older GM SI series, but when I start the car it doesn't charge until I blip the throttle two or three times and then the volts jump up and the light goes out.

The other folks have given you all sorts of good ideas - I'll add one more - what about a junkyard alternator? You can then see if the symptoms change and if you're interested in rebuilding your own, you then have one to work on.

I also had a starter that would fail whenever it got cold, yet test just fine on the machine once it was up to room temperature.

If it was my car, I'd check out the junkyards for a spare and maybe wait until the batt light stays on solid. That said, it's hard on your battery if the alt is sometimes maybe charging or overcharging or undercharging or ??? - if you wait too long you'll be replacing the alt AND the battery.

Ray

Well, the problem was the alternator! After doing a little more checking I replaced it with a new one (not reman). This was not an easy job as it was raining out and I did it in a borrowed garage since I have a townhouse w/ no garage/carport. Routing the belt is much more difficult than outside on a sunny day because there isn't much light and space is tight. The red light did not come on as it normally does and I tested 14.7V with my DMM with the engine running.

Interestingly before putting the new alt on the vehicle I had it next to the old one and spun them both. The old one spun freely and made a slight grinding noise. The newer one didn't spin quite as freely but was easy to turn and was silent. Because of this I think that it's possible that the bearings were going along with the brushes. Whatever happened when the vehicle warmed up either caused the bearings to spin truer or caused an expansion that allowed the brushes to contact....or whatever.

Thanks everyone for all the help.

Are you using a one wire hookup? That is typical behavior for a one wire regulator for a SI. If it really bothers you, replacing the regulator with a stock Delco one and wiring up the DA plug will get rid of this behavior.

nate

Good on ya... Did you change the belt when you changed the alternator?

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and as a learning experience, open the old Alt and check out the brushes,

or did you have to return the old one for a core charge?

Mark

r?- Hide quoted text -

Aw, c'mon, we need to know how good our long distance diagnoses were :)

nate

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tor?- Hide quoted text -

Well I will say you can be sure it was the alternator. As I said earlier could be the brushes and the bearings. I'm assuming they used a sealed bearing that eventually can go.

om...

nator?- Hide quoted text -

The tricky ones were the early ECS 100 types, which were a POS. They constantly gave trouble, largely because they did not cool well enough. I have seen them spit the ball bearings out the rear, the regulators fry, sometimes the diodes go. I dont know if they lasted long enough between rebuilds to eat us the brushes.

Alternator shops often tried to press on bearings that were a little too small in diameter, for some reason or another.

I did have one of these converted to a one wire situation so that I could swap it out for the Bosch unit on my John Deere. Since this alternator is in free air, and does not have a large current draw, it has lasted well for the 3-4 years it has been in service.

I really never had much trouble with Ford or Chrysler alternators.

Beware of FLAPS remanufactured alternators. I think it is far better, if you can, to go to a local alternator shop and let them do the work. They are a bit more focused on the job I think.

AFAIK (the car's under a tarp and snow) the wiring is as follows:

big red wire off back goes to starter two conductor connector goes to a)ignition switch and b)idiot light and voltmeter

I don't really care, the alt hasn't failed. It's about the only thing on the car I _haven't_ broken. I have a 4 piece camshaft, broken axles, holy radiators, bent wheels etc... but the alt works fine. :)

Ray