i have a 08 saturn aura xe i have a problem that no one can seem to figure out. my entire electrical system dims out when im coasting down hill. alternator is good all grounds are good. it even happens when theres no draw on the battery with everything off it still happens. i would care too much but im planning on upgrade the headlights soon so any insight would be great

Maybe your drive belt is a tad too long and there's slack in it at idle, not allowing a strong pull on the alternator. Maybe a belt 1/2" shorter would help.

maybe batt not holding full charge anymore?
Sounds simplistic, but you did not mention if it (battery) had been tested for a bad cell...

GM had a nasty habit of putting cheap (read 3-4 yr) batteries in their new cars back in the 90's -- don't know if this was still true in 2008 but it wouldn't surprise me. I've seen it with other US manufacturers too.

Per Rube, you can check for belt tension under the hood by checking the deflection and comparing it to the spec (which I don't have); maybe tensioner is failing?

You claim the alternator is good ... have you had it tested, or are you just looking at the voltage when the car is running?

The problem with a description of this nature:
i have a 08 saturn aura xe i have a problem that no one can seem to figure out. my entire electrical system dims out when im coasting down hill. alternator is good all grounds are good. it even happens when theres no draw on the battery with everything off it still happens.
is that in theory it is impossible.
Or
It is not really described very well.
How is it you are telling that the >electrical system dims out<
and
what is no draw?
I know how I describe it.
No draw means NOTHING is under power.
So that means you are coasting down hill, the transmission is in neutral, the engine is shut off. No lights are on, no radio is on, nothing is on. That is what no draw means to me.
You use the word DIM
That to me is interpreted that the lights dim. But if there is NO DRAW, then they are turned off.
Is there a volt meter you are reading?
The bottom line is simply if nothing is wrong with the alternator and the battery, this is not happening.
So something is wrong some where.
Are the battery terminals clean or are they all yucked up.
How about some more information that deals with a better description?

Load Test
Under load test of the battery. Under load test of charging system. Newer cars deliver very little power from the alternator at low or idle rpm's thanks to tightening cafe.

I see a slight dimming in all my cars at idle.

However going down hill at road speed, even with a loose torque converter, you are not at idle. I check alternators at idle with a digital volt meter and they will or have indicated rated voltage output with no load other then the engine running and will compensate and pick up the load when things like all the lights are turned on.
So I can not say that the symptom as described is something I see on anything I own.

Hey man, if you live close to an Autozone or Advance Auto Parts, just take the car there. Ask someone to roll the ARBST tester out to the car and check your charging system. They can test the alternator and the battery for you without you even getting out of the car. You just bring it up to 2,000 rpm and hold it and they'll load test the system. If there's a problem with either the alternator or battery, it usually shows up. They can even test the starter if you want them to, but I don't think it's starter related at all.

tightening cafe?

Corporate Average Fuel Economy

thanks guys for the reply by no draw i mean the radio and the heater is off the lights are auto, the battary is running 14 volts at idle ill check the tension on the alternator belt to see it that fixes it

Posted by: sw2cam
On: 01-21-2012 10:05 PM
Corporate Average Fuel Economy
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Which in my opinion is the reason for the required 5W30 motor oil and the fact that these engines have become oil consumers as they have aged. They are not the only ones from this era that have done that, but they are the ones dedicated to this forum. When the oil is that light and they are driven the mileage the S cars now have on them it is or was expected to cause excessive wear due to too light of a "winter" grade oil or at least as I understood things at the time these were built which is why I do not now or never did use that oil.
My cars do not burn oil. I would have to guess that 10W30 should have been the minimum grade oil suggested then and now and I don't use it either. The Oil Viscosity vs temperature charts say 20W50 suits my purposes and driving conditions and that is what I use year around where I live. In all my cars and engines.
and
@ auraxed08 Given that information and Sw2's comment. Then I wuld have to guess what you are seeing might be normal or if anything a glitch in the Voltage Regulator which is probably part of the Alternator. I would check for dirty and corroded connections and if found clean them and then probably call it as normal.

CAFE is the reason for 5-30 motor oil, the only reason. The dangers of 5-30 can be minimized by pouring in something like MOBIL1 5-30 or moving up to 10-30. Hell Unc and I could run 10-40/15-40/15-50, or 20-50 most of the year with the heat we have. I use MOBIL1 5-30 or 10-30 and change my oil/filter at 10K in the ECOtec and have never had an oil burner. Changed the oil/filter in my S cars at 8K and never had an oil burner.

14v on battery at idle only tells you your alt is likely good.
Doesn't tell you if batt is capable of holding that charge

Nor does it tell you what the all important amperage is.

well stated -- can't believe I missed that one

14 volts at idle by itself with no further testing just basically says as stated that the Alternator is most probably not a problem and also as stated tells noting particularly about the Battery however there are other factors to consider at the same time.
One is that you can increase the loading on the alternator to see if it will follow the loading and that can be done by turning on things like head light on bright, A/C and heater fan to HIGH which if you calculate for instance the amount of current required also says that the Alternator can supply enough current to run things. Again that says nothing about the batteries capability of holding a charge.
But, the symptom is going down hill under a trailing throttle. A battery failure does not present itself as being obvious in that mode. The most obvious failure mode is one of not being able to start the car of which the short term loading can be hundreds of amps. The test for that is generally if you have a meter that is capabile of displaying rapid changes of voltage, if the batter voltage does not fall under 8 volts when starting the car, it is considered to be capable of holding a charge which is also a way on assuming that it is capable of delivering enough current to get the job done. That number can be best seen normally in the winter when the engine is cold. A worst case senerio.
And actually while a voltage measurement does not indicate the current flowing, if the source of the current (the battery) can supply all power needed to run things with out the voltage reading falling off significantly, it can be assumed that what ever the current is, the source, in this case the battery is not a problem if the voltage is not falling off.
While I too prefer an Amperage Meter, a volt meter is adequate to diagnose basic problems with out actually knowing what the amperage is.
Also here in the Valley of the Sun where heat flat kills batteries much to my surprise, battery failure can happen instantanious, in that I just started the car and stopped at the post office and now it won't start. That is a common symptom again assuming it is not a connection problem. Something more commonly seen in the snow belt where wet and cold is a way of life.
It is then theoretically possible to run a car on the Alternator alone with out the use of a battery. It can be done and I have done it.
A bit impractical for the most part and no particular reason to do it unless backed into a corner, but it is doable.
But a lead acid battery failure is not one that shows up as a spike in power supplied to the car when going down hill with a trailing throttle.
The suggestion that it might be normal is at least something to consider as stated on newer cars.
There are many functions taking place that for the most part are not visible to the casual observer. Things such as the A/C being shut off under full throttle acceleration. A feature first seen because computor control electronics were available and can be programed to sense that and through wiring turn of the power to the A/C unit to give a bit more power availble while passing something.
The point being that either the regulator could be set up to sense some trigger to drop it's function going down hill thus seeing a "Dimming" situation. But that generally is visible in the lights of the car rather some other means.
My 2007 Chrysler T&C does that which is the newest car I own. The Saturn does not, a least visibly but it is a 1994, from a different era.
Or the computor could be controlling the Alternator regulator with an "IF" this than shut it down to improve fuel economy thought process. While that is a visible concept it is practically a rather dumb thing to do as it proably is not measurable to the average owner but will irritate them.
It still is a subject of fascination to me to have watched the product fail. Mine has been a satisfying car to own, dealer interface early on was above and beyond expectation, although in my opinion the dealer closest to me now was less than satisfactory and the high light being the day I took it BACK for the estimated repair to the sun roof and the nice boy with the clip board carefully explaine to me why the car absolutle needed around $3000+ of repairs before I took it out to repair the sun roof and other things when I had a $350.00 estimate in my hands. Which turned magically into a $1700 or repair. All this while sitting in the comfortable waiting room listening to an elderly lady complain about the sudden increase in expected costs. That still rankles.
But cars like hyundai started selling well and had brought in a basically cheap 2 box car that drove like a tank. But was cheap and border line homely.
The difference I saw was the press beat up on the Saturn and fell in love with the Hyundai. And personally? I think the no haggle priceing in the long run hurt them.

CAFE is the reason for 5-30 motor oil, the only reason. The dangers of 5-30 can be minimized by pouring in something like MOBIL1 5-30 or moving up to 10-30. Hell Unc and I could run 10-40/15-40/15-50, or 20-50 most of the year with the heat we have. I use MOBIL1 5-30 or 10-30 and change my oil/filter at 10K in the ECOtec and have never had an oil burner. Changed the oil/filter in my S cars at 8K and never had an oil burner.
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No argument with this althought personally I would not use 5W30 mobile one.
The point being that the oil cap on the car says 5W30. The owners manual cautions you to use only that or suffer the consequenses and the dealers stressed the use of it only.
The average it seems buyer, would then get stuck on the concept that using something different would cause things to break. And that persists even to today.
Proper oil maintainence would indeed defer the problems that time have indicated would happen. Had something different be used routinely and keeping in mind that was still the era of summer and winter grade/weights oil be used it is my belief we would not be talking about high mileage oil consumers at this point in time of which there is most probably no repair for. The engines are worn out.
I can remember the dealer down in Chandler recommending 10W30 which was some what unusual at the time. An in depth conversation lead to a story about having a couple of engines fail and Saturn ran an oil analysis and found that the 10w30 was in the car and would not honor the warrentee.
Even though 10W30 was referred to as acceptable in the owners manual.
When I bought my Chrysler new in 2007 it was suggested I attend an owners maintanence seminar presented by the dealer so I did out of curiousity.
The subject of synthetic oils came up and it was flat stated if synthetic oil was used it would void the warrentee as would something other than the 5W30 recommed oil that had big yellow or red letters on the oil cap. The same method my Saturn does.
The oil used MUST be the suggest weight and the recommended oil change interval. So I immediatly went home and changed the oil to Mobil 1 20W50 which is what I pefer for this heat here. I use the change the Filter every 4 thousand miles and change the oil itself after 3 filter changes, thus 12,000 miles. I don't use synthetics in my other cars.
I am not sure that with the mileage they have on them that the cleansing action of synthetics would not cause oil leaks that I don't particularly want to deal with.
My experiance and back yard knowledge basically says, light weight oil causes excessive wear and the manufacturer does not care. The warrenty is up at 30,000 miles in the most case and it is not their problem. Theirs is to off load a new car.
And owners of new cars generally trade them about the time the payments are done with whether they need a new car or not. So the cycle or concept persists.

I got the chance to drive the Fiat 500 2 weeks ago.
I'd take one. It drives out very nice and as I like a coupe, it is one. The car pleases me. Although it was understood that I was not really in the market to buy one I have had 7 calls from the dealer to come down and take advantage of numeous discounts/finance charge offers/sales incentives.
I guess I can appreciate the persistance and if I had some free money and actually needed a new car, that is the first one I have driven in 10 years that I would not mind trading my Saturn for. Which I have decided I would like to paint again and call it good for a while.
But the statement, don't bug me seems to have fallen on deaf ears.
At least the Chrysler dealer has quite contacting me with the "Its about time to buy a new car story"