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Old 06-22-2008, 05:52 PM   #1
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Default Failing alternator?

I've noticed this over the past few weeks. While driving sometimes my battery voltage will read at 12.0v down to like 11.4v

It seems to fluctuate a bit, but usually it's around 13.2v when driving. The other day I was driving down and my AFR guage went out. I looked at the voltage and it read 11.0... then it slowly dropped to 10.0V! Then a few seconds later it climbed up to 13.0v

Is this kind of fluctuation normal? When I have my headlights on it's usually around 12.4v but it will drop to 11.6v every now and then.
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-96 SC2 gets 35 mpg mix city/hw.
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Old 06-22-2008, 06:04 PM   #2
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2003 L-Series 3.0L Sedan
Default Re: Failing alternator?

You can do the easy things first since you've been monitoring the voltages in the car; looked at the belt tensioner if its losing its springiness? If you see the belt flapping at idle or the belt deflects easily depressing it between the pulleys then it may be a worn tensioner allowing a slipping belt that won't turn the alternator properly. Be sure the belt is taut then check all the battery connections for corrosion and loose terminals including the ground. Even with lights on the battery voltage should be holding steady at approximately 14v, not 12v, indicating the belt system is loose, the alternator is failing, or poor cable/connection problems.
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Old 06-22-2008, 06:09 PM   #3
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Default Re: Failing alternator?

Thanks for your input. I pushed on the belt and it gives way a bit. Maybe it's stretched. I noticed the tensioner pulley was rather rigid when I last took the belt off.

I have a used tensioner pulley here I'll replace it with a new belt as soon as possible. THANKS!
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Old 06-22-2008, 06:48 PM   #4
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Default Re: Failing alternator?

Although I didn't point it out clearly, the battery and cables are just as important in the scheme of things. A poor battery won't hold a charge while corroded cables (outside and inside the heavy terminal covers) may not be secured enough when connected to the battery. Broken battery terminals have popped up from time to time leading to acid damage under the cable terminals. Removing the RED cable for a close-up inspection under the cover may reveal wetness from a broken battery terminal if it isn't obvious on the battery. Allowed to stay this way and the acid eats away the copper wires inside the cable where its crimped onto the ring terminal. A ruined cable and battery. Be sure to look over the battery and cable connections. If you se or feel wetness, dissolve and neutralize the acid with a solution of warm water and baking soda; the bubbling action is neutralizing the acid that will corrode metal eventually. Toothbrush the area with the solution. Don't allow this to get into the battery with fill caps; it will kill the cells rendering the battery dead. Just rinse everything off with water.
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Old 06-22-2008, 07:25 PM   #5
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Default Re: Failing alternator?

The battery is great (Optima redtop, about 2 yrs old). Before turning the car on the voltage reads 12.0V every time. (except on days when it's really cold, but that's been a while!)

The cables look good to me. No noticeable corrosion. I checked that first.
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Old 06-22-2008, 09:20 PM   #6
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1998 SC2
Default Re: Failing alternator?

You have a major electrical problem. Put the Optima on a slow charger, they do not take kindly to fast charges. Try to find an automatic 2 amp charger. going down the road the battery/system voltage should be 14.2 to 14.7 with no hiccups except when at idle and then it should be above 13.2V. the possible problems are the big red and black cables on the battery leading over to the engine ground and starter motor. Either dig up a real good DVM and measure the resistance or, with the engine running at 1500 RPM or slightly higher measure the voltage drop on each cable. It should be very low, like zero, if any more than that its new cable time. To do the voltage drop put one lead on the battery connection end and then the other lead on the other end of the cable. If you use a DVM the polarity will not change the reading. A good auto ranging meter will cycle down to millivolts and you will see some small value. This is as it should be. If that checks out then with the engine off unhook the fusible link from the starter and then measure the resistance of the link from the alternator to the tab. It should be about 1 ohm. While watching the meter pull on the link to check for a break in the wire. If Ohmeter goes to open circuit you need a new one. All that leaves is the expensive part, alternator. How old is it? If you are lucky there is an Automotive Electric shop in your area and they can rebuild it while you wait for about 1/2 of the NAPA - AZ cheap price. Your symptoms tend to point towards the alternator. Check the condition of the alternator regulator plug also.


The nice thing about most electrical problems is they do not look bad, even when they are.
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Old 06-22-2008, 11:41 PM   #7
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Default Re: Failing alternator?

I think a common failure mode for old/hi-mileage alternators involves intermittent charging due to badly worn brushes for the rotating field.

A bad regulator module might have same effect.
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Old 06-23-2008, 01:24 AM   #8
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1998 SC2
Default Re: Failing alternator?

Brush failure is a possibility but they normally just slowly go away and the output decreases to the point that the battery voltage (nominal 12.8) exceeds the alternator output at some engine rpm and the red light starts glowing dimly and gets progressively brighter. As the battery slowly goes dead. If you find the terminal voltage of the battery reads 12.0 volts with the engine off it is a bit less than half charged.

Solid state regulators have two main failure modes with this design regulator. Full output at all times, which promptly boils the battery to death. Or, no output which turns on the idiot light. The rare failure is a minimal output that just keeps the light off as it continues to degrade as the battery slowly goes dead.

Either way the alternator has to come out for a bench test at a good shop. That usually rules out the local parts seller.

If the alternator is 3 or 4 years old and is subjected to heavy loading the brushes are marginal. And if is a mass market rebuild, no matter which warranty you bought it is very close to bearing failure time also. They use very cheap bearings.
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Old 06-23-2008, 01:28 AM   #9
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1998 SC2
Default Re: Failing alternator?

One more little thing. One of the wires over to the regulator is the battery voltage sense wire. If it has a dirty connection the battery will over charge and if it is open then the alternator output will be low and the battery will be under charged.

And, the belt could be shot and slipping.
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Old 06-24-2008, 12:15 AM   #10
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Default Re: Failing alternator?

Thanks for all the input. As far as I know it could be the original alternator and this car has almost 160K miles on it.

There was also an oil leak and a LOT of spraying oil, some of which went on the alternator. I'm pretty sure I got that taken care of, though there seems to be drips on the coming off the subframe around the passenger side rear bolt.

Maybe my oil pan at the timing cover is leaking on to the crank pulley and it's flinging it in that direction. The voltage was really bad this morning. It was 11.8v at idle almost all the time. This afternoon seemed better. 13.0v+ at idle.

I'm going to replace the belt and tensioner pulley tomorrow and have a close look at the alternator.
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-96 SC2 gets 35 mpg mix city/hw.
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Old 06-24-2008, 01:02 AM   #11
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Default Re: Failing alternator?

I'm inclined to think that your (original) alternator is due for replacement now that you've mentioned it. A worn alternator, if allowed to age gracefully, will eventually wear out the brushes that can give fluctuating voltages similar to a slippng belt from a worn out belt tensioner. At the high mileage you have, there is a very good possibility of all three items being worn out. The brushes worn down in the alternator and the bearings from the tensioner and idler. When removing the belt rock the pulleys from side to side; good bearings won't allow rocking while worn out ones will and spin with noise from lack of lubrication after so many years. Worn bearings won't allow pulleys to turn under a tensioned belt and eventually drag, leading to belt wear and eventual destruction if the early morning squealing doesn't give you the warning message. The alternator can be tested at good auto stores before replacing it.
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Old 06-24-2008, 12:06 PM   #12
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Default Re: Failing alternator?

Well I replaced the tensioner w/ a used one I had lying around and a new belt (that measured a little bit shorter than the old one).

The belt seemed to depress about the same between the idler pulley and the AC compressor. There was oil everywhere! It's just a fine coat... it seems to be leaking from somewhere on the timing cover and dripping onto a pulley (most likely the crank pulley). Oil loss is minimal though despite what is visible. After 350+ miles the oil MAY have dropped a 1/4 qt at MOST, but this morning after measuring I didn't notice it below FULL.

Anyway, started the car up and voltage jumped to 14.1v (haven't seen that in a while!). It stayed at that for a few minutes as the car warmed up and then dropped down. As I was driving it eventually settled at about 13.2v. At idle would be 13.4v avg. I don't know WHY it did that but... that's what it did. I never saw it drop below 13.0v but I didn't have my headlights on (which would have dropped it into the 12v range for sure).

I did clean all the pulleys w/ brake cleaner and most of the oil off everywhere. Maybe that's stopping it from slipping some along w/ a nice new dry belt.
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Old 06-24-2008, 12:32 PM   #13
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Default Re: Failing alternator?

Is the a/c compressor clutch covered in oil? Slimy all around the pulley side? If the oil doesn't seem to come from the cam cover its from the leaking compressor front seal!? This may be oil leaking onto the belt and allowing it to slip. The alternator should always be outputting above 14v, not below. Now to isolate where the problem lies.
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Old 06-24-2008, 02:37 PM   #14
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Default Re: Failing alternator?

Quote:
Originally Posted by fdryer View Post
Is the a/c compressor clutch covered in oil? Slimy all around the pulley side? If the oil doesn't seem to come from the cam cover its from the leaking compressor front seal!? This may be oil leaking onto the belt and allowing it to slip. The alternator should always be outputting above 14v, not below. Now to isolate where the problem lies.
The pulley itself didn't look very oily. The actual alternator looks like it has some oil/sludge on and around it.

I KNOW the oil isn't coming from the cam cover. It might be the front seal. I'll try to replace that soon (was going to when I changed the timing cover but they didn't include one in my gasket set. ).

I have some pictures I'll try to put up tonight.
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Old 06-25-2008, 10:37 AM   #15
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Default Re: Failing alternator?

It doesn't look too oily. Voltage has stayed above 13v the past few days.

A friend suggested I measure the voltage when running w/ the negative battery cable disconnected so I can see actual output of the alternator w/out having to charge the battery. I'll try to get a DMM from work and try that out.

When I first got the car I had a 2200 watt stereo system in there. I'm sure that put some drain on the battery and alternator... haha. It was only in there for about 6 months. Then I had to sell it because my ears hurt too much. >_<
Attached Images
File Type: jpg alt1.jpg (106.9 KB, 35 views)
File Type: jpg alt2.jpg (128.8 KB, 36 views)
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Old 06-25-2008, 11:11 AM   #16
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Default Re: Failing alternator?

sps SOHC,
Take a hold of the fan on the front of the alternator and try and turn it against the normal direction of rotation. It should not turn with as much pressure as you can manage with your fingers comfortably. If it turns either the belt is shoot or the tensioner, or both. With the car running at 1500 RPM or above about five minutes after stating the battery voltage should measure 14.2 to 14.7 volts. If not then you might want to consider a new battery. batteries do not last forever, 3 to 4 years for the majority of them is the normal service life. A failed battery will kill the alternator eventually. And conversely, a bad alternator will ruin a nice brand new battery.
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Old 06-25-2008, 11:50 AM   #17
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Default Re: Failing alternator?

The clearer picture if the two seem too clean with oil everywhere and I'm suspecting the belt is slimy. The entire serpentine belt should be more or less very dry and the picture seems like oil came from somewhere so I guessed the front end of the a/c compressor. If it let go in spectacular fashion the clutch pulley will sling oil in 360 degrees radially. If it sprayed enough oil the belt may be ruined. The belt shouldn't feel slimy or sticky at all but if it does, the refrigerant oil did it. It would explain the fluctuating alternator output as if the alternator were failing. Of course if the belt isn't slimy on the inside then the alternator may be failing.
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Old 06-25-2008, 02:39 PM   #18
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Default Re: Failing alternator?

Quote:
Originally Posted by fdryer View Post
The entire serpentine belt should be more or less very dry and the picture seems like oil came from somewhere so I guessed the front end of the a/c compressor.
Well that's where you are wrong. The compressor was just replaced and I haven't had the AC system vacuumed or recharged yet.

The oil is very clear and clean (just changed the oil a few weeks ago). The belt wasn't dry but it wasn't too oily. Probably more-so than it should be. I would hear it squeal only slightly whenever I was putting on the gas during a turn, so I suspected it was on the PS pulley. It used to leak A LOT (forgot to tighten the center top bolt) but I fixed that. It's still leaking slowly from somewhere though.

The battery is consistently reading 11.8v w/out the car on but it's getting power drawn from the wbo2 heater.
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Old 06-25-2008, 04:13 PM   #19
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Default Re: Failing alternator?

If the battery is reading 11.8 when the car is off then it is is serious need of an out of car slow charge or a one way trip to the battery recycle bin. You are beating a dead horse. If you have oil on the belt then it will slip and the alternator will not charge.

The WBO2 you are referring to is the one downstream of teh cat or have you installed an aftermarket unit? The heater draws considerable current and will kill the battery overnight.
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Old 06-25-2008, 04:54 PM   #20
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Default Re: Failing alternator?

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Originally Posted by OldNuc View Post
The WBO2 you are referring to is the one downstream of teh cat or have you installed an aftermarket unit? The heater draws considerable current and will kill the battery overnight.
It's an aftermarket WIDEBAND O2 sensor and the heater only draws current when the key is in the ignition.

I'll put the battery on a slow charger.
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