Good Alternator But Low Output to Battery

Thank you so much techno. I will clean the ground and get back to you.

No techno, cleaning ground makes no difference.

But this may be a hint of the source of the problem: The charge indicator light does not come on at all to indicate the failure to charge the system. A friend tells me this may indicate a failure of the Body Control Module? The computers involved in the charging system complicate the matter extensively.

Many thanks to any and all who may have ideas for me.

Hello Corneliusvansant

As you say lack of warning lamp may be the problem. Alternator problem was discussed in a thread 30 June 08 in the Electrical Engineering section and this came up = see #4.

I'd add that some circuits have a resistor in parallel with the warning lamp to give initial excitation even if the bulb is blown, but not in your case if this the problem.

Good luck and keep us posted.

Codey

Just read your #3 again and not clear what you mean. Does the charge indicator light not come on at all, indicating blown bulb? In that case need to change the bulb and it should be OK.

If it doesn't come on but bulb is OK, I'd first check that feed to the bulb from the ignition switch is OK (unlikely to be a problem but you never know). Having done that you can check the bulb by switching on and grounding the charge indicator light lead at the alternator.

If all that's OK it's most unlikely that with a new alternator the bulb will fail to come on when connected normally with engine stopped. If it does there's something wrong in the alternator - brushes, field winding, voltage regulator....

Cheers........Codey

I am grateful and on the job. Thank you. Get back to you . . .

Check voltage regulator between battery and alternator; this component convert AC from alternator in DC current @ 13.8 Volts suitable to charge the battery

The Saturn design of alternator has moved the regulator into the alternator.

I don't know if Saturn has addressed this, but in years gone by they had a real problem with alternators going bad. They sited it too close to the exhaust manifold and the excess heat was killing the diodes. Thier response was not to move the alternator or to put any kind of heat shield in between but instead to up the power output of the alternator. In turn, the very next year they upped the current draw on the system as well by adding a bunch of power accessories putting them back to where they were before. I can't say as I'm impressed with Saturn's engineering.

It is entirely possible that your "new" (actually most likely rebuilt) alternator is bad too. You might want to take it to the local auto parts store and have it load tested on the test jig. Most will do it for free.

Thank you gentlemen.

I have heard the same criticisms posted by Rorschats. He has real insight.

It is true that both the alternator replaced and the new one have tested good, out of the vehicle, by Advanced Automotive. To their credit they replaced it again. And we replaced it again - and the problem remains.

We are now planning to replace the BCM unit to see if this works. If not we are stumped again. The cost is getting spectacular.

I owned a Saturn SL2 for 4 years and went through 4 alternators in that time frame. I will not own another Saturn. Ever.

You definitely have a wiring problem, it is somewhere between the alternator and the battery.

You might have a broken earth from the engine to the cars body, that has stumped good guys before now!!!

VERY CAREFULLY, let the engine run and check for voltage drops across each cable one at a time. There should be almost no drops at all, somewhere you have either a bad connection or a bad cable.....you will probably not find it without the engine running, watch out for the fan and the hot exhaust please......

Check the battery by charging it separately and see that the voltage rises....

A good alternator will charge the battery generally up to between 14.4 and 14.8 volts while the engine is running, this will drop down when the engine is stopped.....more is not good, less is not good.......this voltage will only be achieved once the engine has replaced the current used to crank and start the motor......that can take a minute on some cars.....but the voltage should be climbing once the engine is running.

Check your meter against a known good one on the same scale, just in case.....

Read #11 very carefully. Why do you think that all of the alternators have worked on the bench, and not on your car? What has changed since your car worked correctly/ This might also give you some clues as to what is wrong with your car.

If alternator can not output correct voltage, its not working properly. Get a new one. Check output as close to alternator as possible if you got high voltage then you got bad wire to battery. If voltage is about the same, new alternator.

Remember how alternators regulate voltage, they do so by altering the voltage on the field coils using a regulator that must be referenced to ground. If the ground reference is bad, then the voltage sent to the field coil will not be the voltage the regulator thinks it should be. I would go though and make sure that there is no corrosion on any of the brackets or the ground connections anywhere along the path. If you have a high resistance anywhere in the system, you will alter the voltage that the system outputs.

If you ever use jumper cables please do it this way or you will definitely have alternator problems regardless of what kind of car you own.

1. Make sure your car is not running.

2. Connect the cables being positive about the polarity!

3. Wait about a minute.

4. Try the other car. If it doesn't start quickly -- stop.

5. Now start your car and wait about 5 minutes. Do not try to start the other car yet! Don't race your engine, especially in the first few minutes of connecting the cables, because the dead battery may draw a large amount of current initially.

6. Turn off your car, then try the other car again. If it doesn't start and the starter starts to slow noticeably, stop and repeat step 5. It may be best to wait for the other car's battery to charge longer this time.

Do not under any circumstances start your car and try to crank the other car. That is almost a guarantee to blowing the diodes out in your car because a normal alternator will attempt to maintain the voltage and will do so at large amounts of current.

The advice about the diodes and regulator given in other posts is good. If the electronics is in a high heat area, move it even if you have to hire someone. Just make sure they are experts or you could buy yourself even more problems!

Good luck,

Gentlemen.

As usual, the quality of C4 knowlege and insight is outstanding. Thankyou.

But as of now the problem is beyond me and into the hands of Saturn. So far corporate has been cooperative regardless that it is out of warranty.

As of now, it is inoperable without the battery being charged independently. The alternater (twice this week) and the battery each have been changed 3 times, the bcm module twice, the PCM (main computer) once and more.

these problems have happened all over the country with numerous journeymen attempting to solve the problem. There have been electronic problems - odd ones - like erratic cruise control, lights and intermittent operation of devices from day one. There were mechanical problems as well but we will reserve them for another day. It is a shame because the other three Saturns in our family are great.

Again, I don't know about today, but back in the day, Saturn had a quiet warranty extension on the alternators. The TSR recognized that there was a problem and they had a high failure rate so when the alternator was replaced (under warranty, regardless of how old the car was) instead of replacing it with a 90 amp unit, it was replaced with a 98 amp unit in the hopes that the extra margin would allow the diodes to run just a teensie bit cooler, hopefully cool enough to last a while, but it was not to be, even in that model, the heat was just too much.

But like I said, the very next year, the SL2 came standard with an all electronic dash, electric seats, and a bunch of other electronic gew-gaws, eating up that 8 amp margin plus some. But the engine and alternator placement was unchanged. It was the same car with slightly different sheet metal (ok, plastic) and a different interior package.

Saturn's electrical engineers and industrial designers are freaking morons and should not be allowed to play with their daddy's tools. They had some nice ideas, but the execution was a disaster.

edit: I will add that an owner in michigan or the NE seaboard might not have experienced the same problems with Alternators that we down here on the gulf Coast did simply because of the different climate. Up north, I'd bet that there was little problem because the ambient air never gets above 90 F.

these problems have happened all over the country with numerous journeymen attempting to solve the problem. There have been electronic problems - odd ones - like erratic cruise control, lights and intermittent operation of devices from day one. There were mechanical problems as well but we will reserve them for another day. It is a shame because the other three Saturns in our family are great.

This is typical of a bad ground. You would have to get into the wiring diagram and find where the common ground for all effected equipment was. It could also be the ground for the computer.

Good luck!

You sure these electrics aren't made in Italy in the '60's?

Sounds like the problems we had with Magneti Morelli stuff about then.

Stuff made by The Prince Of Darkness (when he was) was about as reliable too.

Just a thought.

Stu.

"I replaced the alternator in my [four year old] 04 Saturn Vue because [when measured anode to cathode at engine idle] the [meter indicated] that battery [charge EMF at only] was receiving only 11.4 volts [...] and the battery [subsequently became fully discharged] failed. but [However, even with new alternator and new battery,] the new one [battery] registers [tests just] the same [...] and my [new] battery is now [also] dead...after just being replaced. [I have tested and] Tthere are no [discernible] paracsitic draw-downs. Help - I am stumped"

Out of kindness I'm going to assume you didn't do this in the haphazard (backward) fashion indicated by your description...but it doesn't really matter since now we can assume also that the battery and alternator are both good, and not the problem.

Now you need to disconnect the ground cable from battery cathode and test resistance from clamp to connection point on the engine. High resistance will be an indication that core corrosion within the cable (not remarkable with original cables at 4 years vehicle life) is presenting excessive resistance...leading to (both) the diminished recharge voltage and to the apparent rapid depletion of battery charge after starting and running the engine. (Or you can follow form and just replace the cable.)

If this (in combination with recharging the battery on a charger) does not fix your problem, take the car in for diagnostics service...

Hi I have been working on Neil's Vue. Maybe I can shed a little more light on the technical side of things. Failed alternator test with Midtronics Tester (industry standard)12.11 max voltage. Replaced alternator, no change. This alternator and engine are made by Honda. Checked voltage drop on both battery cables within spec. 0.01 on both cables. This has 2 wires from computer (pcm) to the alternator. One is an on/off signal from pcm, the other controls duty cycle at idle and at high speeds. On the duty cycle circuit I measured a 1.6 V pulse and on the the on/off circuit I measured 9.6v which was battery voltage at the time. I suspected the alternator to be defective, replaced it with a bench tested alternator. Still not much of a change. Between alternators I made an overlay harness from pcm to alternator which did not make a difference. I worked for Saturn for nearly 10 years and quite some time for VW, I have seen some strange things but this one is driving me crazy.

What would happen if you were to feed 4.5 volts from three D batteries to the duty cycle connection on the alternator. Saturn should be able to tell you what the voltage going to that terminal should be. Also weather it is Dc, Ac, or pulsed Dc. What is the signal sent to that terminal when the alternator is on the test machine? What happens if you send that signal to the alternator while on the car?

Is this alternator used on any vehicles that do not use a duty cycle circuit?

Way back in 1969. General Motors' introduced their first Internal regulator style alternator. Those alternators, and the later upgraded units are very affordable, very reliable, and very easy to retrofit to almost everything.

One of the largest supplier of military vehicles to the U S government has started to replace the 250 amp monster alternators with twin 165 amp Delco units.

If Saturn is a division of GM, WTF is a Honda alternator doing in a Saturn?

The voltage at the alternator terminals should be measured. It should be 14V with a good charged battery and engine running. If this is good then check alt. Neg to batt neg for voltage drop and the same alt B+ to batt B+. Cor has already checked the earth strap but that was an unlikely cause as tis is the same path for start current which is >200A whereas the alt current is likely to be in the order of 50A

I found it interesting to see that the Vue has a computer input to the alternator. I have never seen this on a roadvehicle although we do see them on marine engines occasionally.

Obviously the ON signal will need to remain connected but could the duty cycle input be disconnected for a test? What is control mode of the duty cycle? Is it a simple pwm system or is it a digital signal going to a processor in the (intelligent) regulator?

Lastly, do you have another car you can do coparative tests on?

Thanks again to all, especially Jim

The good news is that Saturn corporate called and promised to do all they could to resolve the issue with the dealer we brought the Vue to. I will post any final resolution.

Pcm input to the alternator is pretty common. I was unable to locate proper specifications though Saturn Technical sites, Honda, or Alldata. I am ASSUMING the duty cycle is pwm because the pulse was consistantly 1.6 V. The on/off signal was equal to the deminished battery voltage at the time. The heavy lead travels from the alt. to starter where the cable contacts the battery cable Pos. and then onto the battery. The vehicle is currently at the dealership further testing is not posible at this time. But, I was the lead technician there, and I still know some of the guys there. I am trying to figure it out for piece of mind.

P.S. Honda traded X number of engines for diesel technology from GM and retrofitting is not possible due to location and space

Thanx, Jim

How much of this vehicle is a Saturn, and how much is Honda? Are there any non Honda engines used in this vehicle? What is the voltage at that terminal on the non Honda engines? For that matter, what is the voltage at that terminal on a working Vue?

Engine and accessories and I think the trans also. The four cyl. is GM. I don't have another vue to compare. I no longer work at Saturn.

If the 4 cyl. is GM, what alternator is used on this?

Get on the ball now. Go take a new one for a test ride. You should be able to get the answers we need in a 15 min. ride.

There is no need to be rude. This is a 2004 vehicle it is 2008, engine combinations have changed in 4 years and so has technology, wiring diagrams, and even harness routing. Are you new to the automotive business. And I think the salesman would flip out if started pulling out a dvom and pulling on wires. The 4 cyl is all GM including the alternator and the honda engine is all honda including the alternator I thought I made that clear.

This may be too late as I just saw your post. I am an auto Starter and Alternator repairman, Which of course qualifies me for nothing. Anyway have you had the alternator bench tested? Did you charge the battery BEFORE you installed the alternator? It does matter. Two thoughts come to mind, (1) bad diodes will cause a low output from the alternator but will still show some output, maybe just enough to cause the light not to work. typically a working unit will only produce enough voltage to maintain the battery "if" battery is charged. When a load is added then voltage will increase to compensate.

(2) As has been stated you have a bad connection in the system. A typical battery connection runs (pos) to the starter, form there to alternator (large wire) with a smaller wire to the ignition switch. Neg wire from battery to some point on the engine. All or any one of these could be weak, just enough to start (with difficulty at times). Also I should note if you did not charge the battery before installed the alternator you may have caused your own problem by killing a new alternator. (i e shorted diodes). Have you checked the battery for problems? A bad battery will cause all kinds of crazy things to happen.

This has 2 wires from computer (pcm) to the alternator. One is an on/off signal from pcm, the other controls duty cycle at idle and at high speeds.

The above is a quote from post 21. When this style alternator is tested on the "bench", what signal is sent to the duty cycle terminal? This has been measured at 1.6 volts when not charging. What needs to be here to cause the alternator to charge? If you can supply this information, you will get the gold star.

Battery was fully charged and two new alternators were installed in succession as stated above.

We deposited the vehicle at a local Saturn dealer on Tuesday and as of 10:30 Friday there is still no diagnosis.

To the credit of Saturn corporate, they are cooperating and encouraging the local dealer in Toms River NJ to find and repair the problem. The dealer's service department has made it clear that they are not happy.

But Saturn customer service corporate agents have been courteous and anxious to solve the problem even though the car is out of warrantee. The car has had a continuous (expensive) history of electronic problems and it is now inoperable.

Thanks again to all. I will keep you all posted as to the resolution.

Cornelius,

Coming in on the end of proceedings and having read all the posts, I can only suggest at this point that the problem is caused by a fault in one of the harness multi-pin joints.

I have a mate here in a national roadside assistance organisation and he told me years ago that most of the causes of roadside breakdowns are due to faulty connections in the pin joints. Like 68%.

As you're not getting any solution to the problem from other directions, maybe you could suggest this to the dealer.

I personally have found faulty pin-to-cable crimps. Sometimes the conductor cut through entirely.

See how you go.

Cheers,

Stu.

More specifics, please:

• What warranty? Saturn limited warranty? What is your Saturn's mileage?
• You mentioned battery (presumably two batteries) that were "fully" charged and were discharged. You said there was no current sink (presumably, when you measured for voltage between ground cable and battery cathode), so the battery(ies) must have discharged by running the car (ignition, accessories) directly off the battery. Correct?
• What did the service department in Tom's River say they will do to diagnose the problem?

I'm confused again. Are you guest #20, 21, 25, or 28? I don't think you are my friend Guest # 30 because you would have asked these questions then. Or are you a new guest? Are you able to answer the question still on the table? That is "what should the voltage signal be at the duty cycle terminal at the alternator?"

So many questions. So few answers.

Sorry, Bob. In posting in response to Cornelius I did not consider what bearing your personal perception of friendliness might have; and my post was certainly not meant to step on yours, if that's what it seems like to you. Since my questions were pointedly directed towards points in Cornelius' last post, I am at a loss to see how they would have been appropriate earlier on. I am solely Guest#20, and then as now, I have attempted to get a better description of just how it is that Cornelius's car problem has manifested itself...so that suggestions can be offered with less guesswork as to what the failure is and how it first came about. Cornelius's post to which #30 responds was with the view to providing suggestions (1) as to what is probably going on to cause the perceived resistance at the service department in Tom's River; (2) possible unseen motives behind the manufacturer's ostensible good will; (3) how it is that the manufacturer might, still, actually be acting on the basis of warranty; and (4) how Cornelius might prepare himself if, in fact, he is actually being jerked around under the pretense of concern from the manufacturer (as suggested by my retitling of my post). It was solely in order to provide such advise that I asked for further clarification about Cornelius' last post. Again, no slight towards you or your posts was intended.

Guest#20/30.

Well now that you have cleared up the question of which guest you are, everything is clear. And you have brought up another good point. I would hope that by now Cornelius has established the name of a person from the Saturn Corp. that is willing to take responsibility for the incurred expenses. I have way too thick a skin to be offended by anything you have posted. It is just that it was getting confusing as to who was who. Thank you for clearing up which guest you are.

Hello Cornelius

This is Codey, not logged on.

Sounds like you're still having problems. Can you clarify a couple of things? Is it a regular, modern alternator with built-in (9-diode) rectifier pack and voltage regulator?

Sounds like the BCM and PCM have something to do with it, have we established yet what inputs from there the alternator needs in order to charge? (as per various posts)

Alternators I'm familiar with are self-contained units and if it's OK and you make the right connections and spin it reasonably fast (say > 3000rpm) it will charge (~ 14 volt, as others have said). If the BCM/PCM complicates things, is it possible to bypass or disconnect this and run the alternator the good old-fashioned way? I assume the BCM does something via inputs to the voltage regulator, so perhaps fitting an earlier type regulator or earlier model alternator is the answer. Maybe not ideal but better than having the car off the road.

What came out of the charge indicator lamp investigation, which you mentioned in #3 and I commented on in #32 and #33?

Cheers.........Codey

The following is taken from Saturn's own technical service bulletin.... Evidently they have seen this problem a lot. Notice their answer is to "do nothing" and that this is "normal". I guess none of their engineers are sitting in a dark parking lot waiting for a jump start. My advice would to have your battery load tested to make sure it is good, make sure there are no wiring problems, and check into a performance alternator at your local speed shop that will keep up with the huge electrical load that these vehicles produce.

Here is an exerpt from the bulletin.....

Any vehicle may have a low voltage display (if equipped with gauges), lights that dim at stop lights, slow cranking, no start, low generator output at idle or dim lights at idle when electrical loads are heavy at idle or under slow driving or infrequent usage conditions. These characteristics may be more noticeable with customer added electrical accessories, or with a discharged battery. These are normal operating characteristics of a vehicle electrical system and no repairs should be attempted unless a proven fault has been diagnosed.

During normal driving conditions, when engine speed is above 1000 RPM, the generator is designed to do two things:

Supply the current necessary to operate the vehicle's originally equipped electrical devices (loads).

Recharge/maintain the battery's state of charge.

The following factors may affect generator and battery performance:

Non-usage of the vehicle for extended periods of time. The vehicle's computers, clocks and the like will cause the battery state of charge to drop (For example; 30 days in a parking lot and the vehicle may not start because of a dead battery or a vehicle which is driven only a short distance once a week may end up with a discharged battery to the point where the vehicle may not start). This would be considered abnormal usage of the vehicle and the normally expected result for the vehicle battery, generator and electrical systems.

Gentlemen "techno" was the first to have the correct answer and I have rated his answer. The ground cable was bad; replacing it solved all the problems. Apparently this has been with the car since nearly new and Saturn would do well to note it.

Once again, thank you all.

Thank you for letting us know the solution to this problem. Happy motoring.

Excuse me, but #20 was the post that first told you exactly what you should do, and what you did do. Techno was indeed on the right track...short of pinpointing an internally corroded cable. Rather than a detailed scavenger hunt and clamp cleaning, the post which gave the exact specifics for diagnostics (about 5 minutes as opposed to 30 up to an hour and more)...you know the rest. So let's be fair minded at the least.

Not #20.

You don't count.

If you don't care enough to give anyone so much as a made up name, why should anyone else care?

Bob was there, too.

Not 20

I have rated #20 as well. Thanks