alternator problems
 

back in may i had changed my alternator for a remanufactured one from Autozone and it worked up until 2 weeks ago when it went bad again. went back to Autozone, got another remanufactured unit and now it went bad. this time, the battery light comes on only when I'm about 2,000-2,500 rpm depending what accessories are on. is this an alternator problem or something else? AutoZone was giving me a hard time saying it's not the alternators but something with my car making the alternators go bad.

both units were remanufactured valeo 140 amps

A bad battery can cook an alternator.

Testing Required for answers
 

Lets get some real information before you run back to the white box auto parts retailer with another "failed" unit.

Has the charging system been tested on your vehicle?
What is the voltage at idle, 1,500 and 2500 RPM? What was the amp output at 1500 rpm?

Has the starting system been tested in your vehicle?
Starter amp draw?
Battery Load tested (volts and amps?)
Battery voltage at rest (key off)?
Battery voltage at idle?
Battery voltage at 1500 rpm?

These simple tests will tell anyone with auto diagnostic skills, what is going on. Everything else will be Scientific Wild Ass Guess > SWAG, based on personal experiences and other general guessing.

Notes:
Cheaply manufactured Alternators have approx 32% failure rate. A cheap Alternator with a cheap volt regulator installed makes that rate low. In a price driven world of remans, the installer is the first and last step in quality control. :wow:
Many posters have experienced what you are going through. It was their solution to replace the offending alternators with new Bosch units that resulted in solving their issues. IMHO the volt regs are the weak point on most of the white box alternators being sold at the auto part chains.

Stick with OE or OE Aftermarket as the original one lasted 100k.

voltage at idle is 13.5v-13.3v
at 1500rpm its 13.9v-13.7v
at 2,500rpm if the light isn't on about the same as 1500rpm
if it is on drops to low 12v.

i didn't check anything else

and my car had a valeo in it to begin with

Yup, Valeo is the only listed supplier for the E53 3.0i 140amp alternators.

I assume it's the 6cyl as the 8's all had Bosch water cooled ones AFAIK ($$$).

I've read a lot of people go through a few replacements with remans.

As already posted I would check the battery is still good. Other than that, with the symptoms as you describe, I would be suspecting the alternator myself.

The battery is only a couple months old

Try checking the BST (Battery Safety Terminal)

Could be faulty?

These links mught help.

https://www.youtube.com/watch?v=c26Jq1O1m0M

https://www.youtube.com/watch?v=s-XO98LOa3Q

I had an Autozone's Duralast battery that was just a day old when it tested bad. Don't assume that because you replace the battery it must be good.

Thanks for the test numbers.
voltage at idle is 13.5v-13.3v
at 1500rpm its 13.9v-13.7v
at 2,500rpm if the light isn't on about the same as 1500 rpm
if it is on drops to low 12v.

Based on the fluctuation above idle I would return the unit, stating that there is a loss of charging state at hwy speeds and demand a replacement. Then I would make them test the unit before leaving the store. The test needs to show Voltage and total amp output at multiple RPMs. It can not be just volts as that will not show total output.

The numbers show that at idle your alternator is charging correctly.
ANY fluctuation off idle and into higher RPM shows a slip ring, windings loose, or brush contact issue. VERY common issue on rebuilts that have not been cleaned, ground flat, and paint over spray on the contact points. This problem with rebuilt units has been a re-manufacturing issue since the 60's as the cost of quality control and true manufacturing brings the cost to the end user close to new prices. That is why there are so many short cuts and defect units. Once you had the chance to bench test a few defects, you will notice that all some do is clean, paint, and slap a regulator on them after a quick cleaning of the stator along with a bushing or two. A REAL BAD PROCESS but one that delivers a cheap unit with controllable defect rate.

If it was my vehicle or a customer vehicle, I would install a new Valeo unit of the highest AMP output I could find, as it would be 100% new and bench tested. In your case as you are doing the labor each time, you get a simple choice...price or performance reliability.

Next test is the battery condition. Attached is a great write up by a community college tech teacher showing proper methodology and metrics.
Note: You can simulate a "load draw test", by turning on every accessory (don't forget the rear window defroster) on high for a 60 sec hit. You will NEVER get to 250 amps but it will pull the surface charge off the battery for a backyard quickie test.

The tests are always: Key in your pocket, test at battery terminals not under the hood. Then RE-test under the hood to confirm that the wiring and connections are at 0 resistance (or close enough).

Tip 1: Test the large positive jump point on the firewall to make sure it is tight. Multiple people have experienced fluctuations of start/no start issues from this connector.
Tip 2: Check the wiring harness from the alternator and starter for breaks in the insulation and wires chaffing.

Search "VOLT DROP TESTING" and check the cables and grounds in and around the trunk mounted battery.

Bottom line: Test all and confirm "KNOWN GOOD" what is left is what is bad.

Good luck and hopefully this is helpful.

One more note
 

I will bet if you have one of these you would find the current alternator puts out 13.1-14V and 60 amps at idle and goes bye bye at higher RPM and never puts out 140 amps as designed.

I remember reading a tale of woes posted here a number of years ago involving this same white box reman store and a member who was paying something like $150 per fitting for a series of defective reman alternators. The alternators were and, most likely, still are junk and no real savings over a new alternator.
Save yourself the headaches and extra expense and do it right the first time.

I've some good reviews on O'Reilly remans. Any experience with those? Are Valeo and Bosch directly interechangeable, other than the pulley?

Just an update I couldn't do much this past week but I had removed the alternator and it passed the autozone test but didn't have a replacement to give me

Confused???? If the alternator passed the test, why would they replace or exchange a good alternator?

Because I demanded another one

My battery light went from only coming on at high rpm to on all the time. Took it to autozone and it passed their bench test. I installed the alternator back and made sure I checked all connections and as of right now the light only comes on at high rpm again

Have you unlocked the obc and see what voltage the system is at when the light is on?

If it is less than 13 volts you may want to let Autozone take a ride with you to prove that there's a problem with the alternator.

when the light is on it drops to low 12'sv

Without a bench test I am guessing it is the regulator or the slip ring not allowing contact at higher RPMs. Bad alt, period.

There is a posting on the forum of a few bench tear downs that show the internal parts and the carbon build up on the shafts.

took it to an alternator shop and tested bad like i figured. took that info to autozone and got a full refund. and the alternator shop sold me a brand new alternator for $210

Thanks for posting the process you are going through. Painful.

Good luck on the final solution. Let us know if all gets resolved.

Yet another data point to not trust the auto-parts alternator testers. I think the results are useless, and even believe that one time a parts-store bench test actually killed my alternator even more (i.e., was just worn brushes when I took it in, but the machine fried some more ... and I forget details but it may have also told me the alternator was fine :yikes:).

I now rely on on-car voltage measurements and then my own component level bench test. I expect the alternator shop's equipment is just fine, but we don't seem to have those shops any where near me.

Glad you finally got it fixed.

REGULATOR DIAGNOSTICS
 

Greetings,

New here, so I have a question perhaps someone can answer. I have 03 X5 and battery light came on, replaced battery a couple months ago, and now alternator died as there is no voltage coming out of it. This is water cooled monster. Changed one on my 545i a couple years ago, so I broke the old one open and the regulator readings across two terminals was open one way, and not the reverse continuity.

So my question is, I have found that most people say the regulator goes bad, so has anyone done any diagnostics on regulators, as in put meter on connectors to see what the reading is in ohms. I was thinking of rebuilding the old one I have had or just change regulator, but was wanting to know if anyone remembers continuity test.

Thanks

When "the regulator goes bad," I believe it is usually just that the brushes (part of the regulator) wear out. That is easy to see visually once you have it out.

Yours is a water-cooled alt, right? I remember seeing a thread on here not too long ago, where there was a bearing failure on one of those, at a fairly low mileage. You might want to consider that as something to preemptively repair.

Just so you know for the future, the "battery" light coming on is actually telling you the alternator is failing - the "battery" light does not indicate the state of the battery itself but the state of the charging system. :confused:

Given the full replacement cost of the water-cooled alternator, it is likely worth looking into repairing and/or replacing the internal components that have actually failed; as you suggest, the regulator is one possibility, as are the brushes, as mentioned by oldskewel.

REBUILDING WATER COOLED ALTERNATOR
 

Thanks, I am learning as I go, read everything I can on subject, and checked and bearings are not noisy, spins freely, so not knowing what is common problem, figured I would try to learn more before tearing it apart. Not an easy job to pull and change regulator only to find out it may be diodes bad, so will check these too while apart. I bought new regulator, checked continuity and compared to old one, and yes, I have continuity on connector of regulator on old one, but none going both ways on new one, so I suspect this is the problem, so was just trying to see if anyone else bothered checking regulator before wasting money. Sadly, most just keep replacing components without diagnosing, and dealers just want you to spend a grand for new alternator, and I am from old school, diagnose it down to component level first.

Thanks,

Do yourself a favor and avoid a returning headache by just purchasing a new alternator to replace your defective one. So suppose you do the regulator fix, 3 months later bearing whine comes into the picture. Then you will be back at replacing the alternator. By the way why did you not check the charging system when the battery light came on? It would have produced the results of a failing alternator.

NEW ALTERNATOR VERSES REPAIR
 

Thanks, and you may be correct, but I am old retired electronics technician, from the old school, from the repair over replace era. lol It was obvious when the battery light came on that it was alternator as I had replaced battery a few months earlier, doesn't take a rocket scientist to know the vehicle would not run for long on battery power alone. Was able to get home, barely, and battery was dead, wouldn't restart when I put on voltage meter. Charged battery, checked again, only 12.1 VDC while running. Checked connections at alternator, belt, etc., so pretty obvious.

So here was my reasoning, replacing costs up to $600. and a regulator is $60. and diodes are $6. each. So I pulled it apart and bearings are smooth and noise free, no sign of wear at all. Regulator has open circuit when doing continuity test, while new one does not, so I know there is a problem with regulator. Started to check diodes, one had corroded leg which was broken and one was shorted, probably what caused regulator to go bad, so with that, figured I was safe in just ordering the diodes and replace the regulator and in the end, I save several hundred dollars. Mechanics will just try to sell you a new alternator and with labor, hit you for a grand, some of us don't have the money to waste, bottom line, so will update results when I get diodes which I will replace all six given when one goes, they all will eventually.

Thanks,

Nice work, FREE-PPV!
Glad to hear you were able to isolate the actual failed components and replace them.