Why does my battery like come on intermittently?

July 7, 2012 5:52 AM

My 2004 Saturn Ion has been having a problem with the battery light coming on intermittently. What could be causing this issue?

It will typically shut off a few seconds later; however, the frequency of this occurring is making me concerned. I had the mechanic check it out when I last had an oil change, and they tested the alternator and did some sort of software upgrade, but were (naturally) unable to reproduce the problem when they test drove my vehicle.

It seems to most often occur when I am accelerating at higher speeds or going up a steep hill which makes me think it is tied into the load on the engine somehow, but this is by no means the rule. Sometimes it will just flick on for a short time while I am cruising at a steady speed on a flat road.

posted by jamincan to technology (6 answers total)

Others with more specific Saturn knowledge will probably chime in, but to me that sounds like it could be the accessory belt. (Dunno if a 04 Saturn uses more than one belt - if just one, it would be the serpentine belt.)

One thing you can try is separating the issue of load from the issue of RPMs. Under a light load, shift down - the RPMs should go up. Does the light turn on?

On a straight stretch on the highway when you're cruising at steady pace, what happens when you accelerate (but don't cause the transmission to shift gears)?
posted by krisak at 6:09 AM on July 7, 2012

It could be the belt slipping (you may or may not hear a noise when it does this - if it is wet, it will be a possibly muted screeching). This is more likely to happen if the alternator, rather than the engine, is under load. The alternator runs off a belt drive and has no way of knowing if the engine is under load or not, only how much electrical load is demanded of it and the engine speed. Higher load and lower speed = highest chance of belt slippage. Does the light come on first thing in a journey? More or less frequently during a longer drive?

It could be a loose connection within the charging system or even within the charge-monitoring system. If a battery earth (for instance) is loose or corroded, the engine moves under load and breaks or partially breaks the connection.

It could be an internal problem with the alternator itself - again, engines move under load and anything that can move will, which may cause or highlight a problem.

Whenever you have an intermittent problem you have two options. Either someone needs to get into it and check everything (which can be expensive) or you need to experiment (safely) and see if you can reliably make the fault occur. As soon as you find out what forces the fault, you can take it to the mechanic and replicate it. Try experimenting with it and not everything that occurs (always on that hill away from being parked, always at the end of a long journey, more when it is wet, more when it is hot etc., etc).
posted by Brockles at 6:34 AM on July 7, 2012

I've had a Saturn SL and now have a Saturn VUE - so I've been around Saturn service for way too long. Has there been any extra rain in the area? I've found my VUE and my SL2 would both have the battery light do its flicker at high revs when some water had gotten up underneath the hood.
posted by skittlekicks at 7:52 AM on July 7, 2012

Have the alternator load-tested. There is a way they can fail in which they act fine at low speeds and loads, and only fail at high speed/load.
posted by gjc at 10:51 AM on July 7, 2012 [2 favorites]

I have the same car you do... I had the same problem you did.

The alternator is beginning to go. Soon the light will begin to stay on longer and more frequently. Eventually, all your power will begin to fail. I took it to Sears and they said I had "noise in the wiring" which is bullshit even though they said the alternator was fine. Two days later, I am loosing power while driving... dont do this.
posted by handbanana at 11:03 AM on July 7, 2012 [1 favorite]

I believe that the alternator test they did was a load test. They apparently ran it at a range of speeds and checked the charge through that range and it didn't show any issues.

Is there an easy way to check if the belt is too loose or worn? What sort of thing would I be looking for?

Rain shouldn't be the issue as we have had very hot and dry weather here.

I will try to narrow down a consistent situation in which it exhibits the problem. The silver-lining is that it seems to be happening with more frequency, so that should be easier to do. Hopefully I don't end up stranded on the side of a highway.
posted by jamincan at 3:10 PM on July 7, 2012