Battery or Alternator?

[98RedSaturn]

I've got a 98 SL with 188,600 miles on it. Last night my car started and drove fine, no problems starting at all. This morning I wake up to a dead battery. I jumped it and got it going again, but on the drive in, anytime I'd use the wipers, turn signals or brakes, the day time running light would flicker. After I got to work, I turned it off and tried starting it again and it acts like the battery is dead again.

Is the battery or the alternator the problem? Or could something else be causing this?

[dcc81187]

If all you had to do was jump it and it ran it is probably the battery. If it is the alternator once the battery gets drained you can jump it but the car will only run for 10min or so. If you take the battery to an autozone, advance auto, or o'rileys they should load test it for free. Good luck.

[westwind999]

A volt meter will give you a pretty good idea too. You should have over 12V at the battery with the engine off and close to 14V once you get it started. If there are no warning lights on once it's started it is probably the battery but sometimes the alternator has just enough output to put out the warning light.

[madpogue]

A battery just weak enough not to start the engine, but not run way down, will run the engine with no alternator output a LOT longer than 10 minutes. The PCM and coils draw pretty low current. It's when you hit the brakes, turn signals, wipers, etc., that you start to really run it down. In any event, +1 on the voltmeter; buy one before buying a single part.

[fetchitfido]

Buy sandpaper too and clean up all the battery connections. I can't believe how corroded the (+) side was on a '96 SL1 I recently bought, yet it still shifted (in forward gears anyway) fine

[Spaz]

The daytime running light flicker would point more towards the alternator but you really should perform a diagnosis first, as others have said, before replacing anything.

[OldNuc]

You need to test the alternator and battery. You can go to a parts store and they can test the battery and alternator in the car or you can do it at home if you hagve a voltmeter.

First check teh battery voltage with teh car running at 1500 RPM, should be 14.2vCD to 14.7vDC. Then turn it off and let it set for a couple of hours. Now check the battery voltage, it should be 12.8vDC and no lower than 12.6vDC. Those are absolute values, close will not catch it. It is probably going to turn into a bad battery and a bad alternator both but its best to check.

[westwind999]

I'm thinking it's possible a battery at 12.4V or so may just need to be charged?

[OldNuc]

If you let the battery set for 2 to 3 hours after a decent drive and then it reads 12.4vDC stick a fork in it, its done.

[Fallguy]

Typically if measure your battery voltage with the car running and its well into the 13 volt range or even low 14 range your alternator is doing its job and stuffing electricity back into your battery.

If you are not getting into this range with the engine running it is likely your alternator.

If you are getting into this range (say 13.6-14.4V running) then it is likely your battery (shorting itself out as it sits).

This is approx info but this is what I would look at first. Buy yourself a load tester on sale at harbor freight or have one of the autoparts stores do a free load test for you.

If you use a voltage tester (cheap one will work fine) make sure the scale is set to DC voltage and at the closest range just over 12v to get accurate readings.

Good Luck.

[OldNuc]

First check the battery voltage with the car running at 1500 RPM, should be 14.2vDC to 14.7vDC. Then turn it off and let it set for a couple of hours. Now check the battery voltage, it should be 12.8vDC and no lower than 12.6vDC. Those are absolute values, close will not catch it.

If you deviate from these test instructions you will be wasting your time as the values you get will tell you nothing definitive. The purpose of this little test is to verify the condition of the battery and alternator.

[98RedSaturn]

I had to jump it when I left work on friday and drove it home with the same flickering problems. When I got got close to home, I would turn on the a/c on high, headlights, air circulation, anything at the same time to see if it would effect the battery. Nothing changed except the battery light in the dash would come on for a second. It was dead again after I turned it off when i got home.

I brought the battery in to get checked, since i didn't have a volt meter. the battery is bad. The guy said it has a dead cell.

We'll see what happens when a new battery is put in, if the alternator effects it at all.

thanks to everyone for your suggestions.

[OldNuc]

A "dead cell" can ruin your alternator also. The red light on the dash will not tell you this either. Go to NAPA, AutoZone, Advance, or O'Reillys and get your alternator tested in the car. If the alternator is bad it will ruin your new battery.

[Growser]

If the alternator checks ok, also check your serpentine belt and it's tension. You need the belt to do it's job in order to turn the alternator.

[OldNuc]

If you do the in-car load test that will tell you if the alternator output is lacking. As you have your face in there when you run the test you usually spot a bad belt/tensioner. If the belt jumps when you apply the load and again when it comes back off you pretty well know its a belt problem.

[Oh3dakota]

i had the same prob too.. all th lights would flicker inside and out of the car .. My neg batt. terminal was loose .. make sure all your cales are tight

[jcasekim]

1998 SL2 AT. Don't have any problems starting or dimming lights, but my transmission started showing mild reverse slam last week, plus rough upshifts from 3rd to 4th and rough downshifts from 4th to 3rd if I do it under pressure (like slam the accelerator while going uphill). After changing the fluid twice and the filter once with a Saturn OEM filter (and having replaced the valve body with a rebuilt one 5 months ago), I wondered if it might be an electrical problem.

Battery is fairly new but alternator is original (11 years, 163,000 miles). Yesterday Kragen tested the battery and alternator in the car. Right after driving, they said battery voltage was fine (high 12's) and alternator was fine, though their tester didn't give the alternator voltage at 2000RPM.

Went home, waited 90 minutes and tested battery myself, read 12.7V. Started car and alternator read 14.07V at idle (800-900 RPM). That's below OldNuc's spec (14.2V minimum), but I couldn't test it at 1500 RPM.

Do you think my alternator is fading and that could be causing my shifting problems? Or I won't know until I test the voltage at 1500RPM? If I'm putting load on by turning on headlights, heater fan, and rear window defroster, do I do that at idle or at 1500RPM?

--John Kim

Originally Posted by OldNuc

First check the battery voltage with the car running at 1500 RPM, should be 14.2vDC to 14.7vDC. Then turn it off and let it set for a couple of hours. Now check the battery voltage, it should be 12.8vDC and no lower than 12.6vDC. Those are absolute values, close will not catch it.

If you deviate from these test instructions you will be wasting your time as the values you get will tell you nothing definitive. The purpose of this little test is to verify the condition of the battery and alternator.

[OldNuc]

You should be able to stick a wedge between the throttle stop and throttle arm right at the throttle body to get to 1500 RPM. If you just turn the black cam on the throttle body you will se where the piece of wood goes. A sliver of wood shingle works well. A screwdriver will end up falling out into the parallel universe that exists between the top of the engine and the ground, never to be seen again.

A reading of 14.07vDC at 800 RPM is not a disaster but it does sound low. Just checked one and with the DRLs off (e-brake on) and the radio on from a cold start to a stable idle at 850 I read 14.15vDC on the battery. As soon as the RPM goes up the voltage goes above 14.20vDC

It does sound like you might have a bit of an alternator problem. The 12.7vDC on the battery should be OK. If you can let it set overnight and check the battery before start you will have a better idea of battery capacity.

[jcasekim]

Thanks, OldNuc. Didn't have a shingle and Home Depot contractor pencil was too thick, so used a takeout chopstick.

Cold battery after sitting overnight: 12.56V
1500 RPM no load: 14.36-14.43V
1500 RPM heavy load: 14.24V

My "no load" was no DRL, blower fan on lowest setting. "Load" was blower fan on highest setting, radio on, (soft), headlights, and rear defroster.

So it looks like I do not need a new alternator, at least not yet? And more importantly, my transmission problems are probably of the solenoid or input shaft nut type, not electrical?

(I did drop something off the battery and it disappeared into the parallel universe, but later I found it wedged between the lower part of the transmission and part of the subframe.)

Originally Posted by OldNuc

You should be able to stick a wedge between the throttle stop and throttle arm right at the throttle body to get to 1500 RPM. If you just turn the black cam on the throttle body you will se where the piece of wood goes. A sliver of wood shingle works well. A screwdriver will end up falling out into the parallel universe that exists between the top of the engine and the ground, never to be seen again.

A reading of 14.07vDC at 800 RPM is not a disaster but it does sound low. Just checked one and with the DRLs off (e-brake on) and the radio on from a cold start to a stable idle at 850 I read 14.15vDC on the battery. As soon as the RPM goes up the voltage goes above 14.20vDC

It does sound like you might have a bit of an alternator problem. The 12.7vDC on the battery should be OK. If you can let it set overnight and check the battery before start you will have a better idea of battery capacity.

[OldNuc]

The 12.56vDC is low for the battery. That could be from additional electronics. Try and get a voltage reading with everything in the car off including the DRLs. Do that just as soon as the idle drops to 800 after a cold start. With a battery that is dropping off to 12.56vDC the alternator should be a bit higher but the cabin blower load is quite a bit and will cut into alternator output.

It does look like the battery and alternator are a bit on the tired side, but adequate.

Where did the rebuilt valve body come from? Reverse slam is only a valve body issue.

The throttle position sensor has an impact on the forward gear shifting performance. Have you seen any tendency to have a high idle after coming to a stop?