More battery/alternator troubles
 

Recently I have been having alot of problems with my charging system. After replacing the battery and having the alternator rebuilt, it seems I am still having problems. Here is the problem. I checked voltage of battery with car off, read 12.6 volts, with car on only read 12.4 volts. It seemed as though the alternator was not supplying enought current to the battery. But when I disconnect the negative battery terminal, voltmeter reads 14.4 volts at idle. Went to mechanic and explained the problem. He told me that voltage regulator does not supply between 13.6 to 14.4 volts to the battery constantly because that would overcharge the battery. The battery hopefully should have been fully charged, because the entire weekend I drove only during the day, with no accessories on whatsoever. He informed me that it is completly normal for the voltmeter to show low 12s as a voltage reading, if the battery is fully charged, to avoid overcharging the battery. But the problem is that the more load I put on the electrical system, compressor at max speed, headlights, radio, with 2 500watt amplifiers, and rear defroster, the closer that 12.x gets to 12.0. With all these systems on, the alternator read 12.1 volts. This seems like the opposite way the alternator should be functioning, correct?? The higher the load, the more voltage needed to maintain battery supply. Alternator shop said that something is wrong with the battery and that I should have it swapped out, but the battery is only a week old?? What is going on here?? :confused:

What RPM are these reading?

Readings were taken at idle, about 600rpm.

What a load of BS, depending on rpm, load and charge in battery you should have a reading on your volt gauge of at least 13 v, anything less is not acceptable. If you have cleaned and checked all your terminals and grounds, next step would be to check voltage output at the alternator (the big fat terminal) anything less than 13 v would suggest alternator has failed. :)

First thing is NEVER unhook a battery while the engine is running. 2 things could happen and both are something no one would want. First the battery could make an arc and ignite the gases around the battery and cause it to blow up. Second, if there is a problem with the regulator and it is OVER charging you could actually TOTAL the car by distroying all the electronics. SO NEVER unhook the battery while the engine is running.

Now on to your problem.
The voltage at the battery with the engine running and everything else off and fully charged battery should be 13.0 to 13.8 Volts. Domestic cars will be 14 to 14.8 volts.
With the engine at idle, check for AC voltage. It should be less than 1V. If it is more, than the rectifiers are bad in the alternator. Now back to DC volts at the battery, turn on the lights and the AC fan to high. The voltage will drop but it should stay above 12.5V. Rev the engine to 2000 RPM and the voltage should go back up to 13.0 to 13.8 V. If not, check the alt belt first. It should be tight enought that you can't turn it by hand.(Be careful, it will be hot). If the belt will slip when turning it by hand, it is toooo loose. Tighten it and recheck.
Let us know what you find.

Paul's Auto Electric

With the engine at idle the AC voltage read .1 volts. After switching the headlights on and with the fan on defrost, the DC voltage on the battery only read 11.8 volts. At 2000rpm, voltmeter only read 12.1 volts. I was not able to test/tighten the alternator belt tonight, but will have that done by tommorrow. The thing is that I bought the battery only 10 days ago, had the alternator rebuilt 3 days ago, and checked the wiring/made my own wiring harness but got the same results. Alternator shop suggested that something was wrong with the battery, but now I just don't know what is going on.

I went by the mechanic again today and he tested the battery and told me that it was working properly, he told me that something in the system was draining the battery, so I decided to try and determine the cause of the drainage. I read on another post how to go about determining the fuse location, so I proceeded to pull fuses one at a time measuring the amp draw each time. As soon as I disconnected the positive side of the battery I noticed that the voltmeter started at -.400 amps and went up a pretty much a constant rate of about 1/100th of an amp per second. This continued with all the fuses I pulled until I got to fuse #13. The fuse card says that the diagnostic, hazard warning system, clock, central locking system, control unit memoroy of seat adjustment system, and electronic radio are all run of this fuse location. Oh yeah, after having the battery disconnected for maybe only 10 minutes, the voltmeter went all the way to 5.0 amps when I got to #13. I am almost positive that the vacuum pump is the cause of this battery drainage because I started having problems with the driver's side lock around the same time (after a girl rear ended me). I will search for the location of the vacuum pump and provide an update.

"Went to mechanic and explained the problem. He told me that voltage regulator does not supply between 13.6 to 14.4 volts to the battery constantly because that would overcharge the battery."

You need to find another mechanic. This guy is clueless!

Duke

I don't see how a drained battery would have any connection to low alternator output. Did you check the belt as previously mentioned? According to Paul's test below in post 5 you have a bad alternator, or belt is slipping. I would get the alternator tested by someone other than the guy who fixed it, to get a second opinion.

MP

Yes, I checked the alternator belt today, it had plenty of tension. I will have the alternator output checked by another company.

Just adding to what everyone else has said:

With ignition off, your battery output should be a nominal 12V or just a bit over. That is the voltage output of the battery, period. Anything less indicates a weak battery or one that has been drained and not sufficiently recharged.

With the engine running at idle and all accessories off, you should be seeing 13.8-14.V volts. Only the alternator will be providing that type of voltage, not the battery. If you are seeing anything less, then the alternator is not providing enough juice to drive the accessories and simultaneously recharge your battery.

If you have confirm belt tightness, then most commonly, either the voltage regulator has failed or the brushes in the alternator have worn out.

You have mentioned that you are running high watt amps...these require a pretty healthy appetite of current, and the stock 80-amp unit may not be up to the task. Alternators are the first to go when someone brings in a car with a mega-watt sound system that has charging problems.

You might consider upgrading to the high-performance alternators, which are designed for heavy-load accessories. They start at 100-amp units up to 250 amps, and I have seen setups in SPL sound-offs that run several in tandem!

Good point about the high amps. I missed that in the orig post. Those 500W amps are likely the problem. I would yank those puppies out. Those would be more appropriate in a pink Hyundai Sonata with a big spoiler on the back and 12 inch wheels. Or put in 2 more, take out the engine and the car can just bounce down the road.

MP

Nah...I ain't hatin'...I used to compete in sound-offs with my VW...it required a custom high-output alternator and I ran two batteries!

Just saying if you are running 1kW amps, you may be overtaxing your alternator. BTW, their current draw is continuous regardless of your volume setting, and during peaks, power demand most likely forces the system to starve all other components in the car to feed the amps!

Pro competitors use huge capacitors to store excess energy and deliver it when your amps require it under those conditions.

Also, I hope your amps are at minimum being fed by an isolated 5-gauge lead with a 35-amp fuse directly coupled to the battery. Not much other than ABS and other major components require that type of current feed. You don't want to risk blowing a fuse while driving and putting yourself at risk with a major component being disabled.

MB design requires engineering the total package when integrating a new feature. Putting in high-wattage amps requires the same thought process...

I agree with G-Benz 100%. If any car I drive isn't charging at 14.5V I start to wonder what's wrong. Keep in mind that even some all oem cars cannot always keep up at idle, with all the accessories and lights on. It sounds to me like you're more knowledgeable and mechanically inclined than you mechanic, I bet you solve it on your own. It sounds to me that your alt is just simply too weak for your car. Maybe a different more powerful alt, or having the rebuild shop boost yours?
I like doing things different and on the cheap, I’d put a high amp unit from a junkyard chevy in there. The boneyard by me charges $18 for an alt.

I think 14.2V or even 13.9 should be enough.

True, but I like to be in tip top shape. :D
Last week my RV was putting out 19 Volts, that is until I realized my multitester had gone crazy. A check with a new tester and I was right at that sweet 14.5

When I had the alternator rebuilt some of the internal parts were upgraded, not sure of all the names but, shop informed me they could boost output to about 90 amps. How would I go about verifying this. And I think that my vacuum lock pump is draining my battery and causing all my problems. Would it be a proble to disconnect fuse #13 and test the battery voltage, or is their a fuse for the lock pump seperately?? And about my audio system I have 2 Alpine MRD-M500 amplifiers, which produce 500 watts continuous power each and 900 watts max. The amplifiers are turned down though, because my subs can only handle 300 watts continuous. I have a Monster 1 farad cap that supplies the voltage to the amplifiers after it receives it from the battery. About the wire, Moster 4 gauge wire an 80 amp fuse. I would really like to make this alternator work, seing as how I just spent $150 to have it rebuilt last friday. I did look into a custom alternator but after all the custom fabrication necessary to mount it, it seemed a bit too expensive for my tastes, probably close to $500. I have unplugged the amplifiers for now, until I get this whole electrical problem straight. I am kind of surprised that you all are oppossed to the idea of amplifiers in the car. Subwoofers are the best. It is like torture listening to music through those puny 3.5 speakers!!

You could take it to a parts store chain like Kragens or PepBoys, they usually have testers. That or you could probably rig some guages and do it yourself.
90 amps is pretty good if it can really do it, but I doub't it, plus you do have a lot of stuff going on. I can't say about that pump since I don't really know what you're talking about, but I'd disconnect it.
I've put non oem alternators in cars before the ones I did weren't too difficult. Some just needed some washers to shim 'em up right, others need a custom nount. I made a custom job just a few months ago, it came out awsome. I also made an AC compressor mount for my truck; Toyota Tercel AC on a Chevy V8. :rolleyes:

I love amps myself, butt news flash: I've never seen an amp draw what its rated output is. My last car/amp setup was 700 watts which would require maybe 60 amps or so of draw. The fuse was 30A and never blew.
I'll never forget my very first amp and its lesson in wattage; it was rated at 300W, but came with a 5A fuse!

I'll bet Willy Nelson sounds superb on that system!

I agree! Sounds like you did your homework as far as your system is concerned.

I had to quit stuffing subs in my cars when I got married and started a family. :( I don't particularly care for the pathetic OEM systems offered by MB (or anyone else), but I get to have my butt kicked every weekend by my arsenal of bass cabinets when I'm playing with the band! So, it's a tradeoff. :musicband

Many amplifier companies over rate their amplifier outputs, but Alpine is not one of those companies. All Alpine amps are tested before they are shipped, at 14.4 volts and the results are included with the paperwork, when you purchase them. One of my amplifiers test at 586 watts at 14.4volts. So I know that Alpine watt measurements are not overinflated, similar to JL amps and Phoenix Gold amps.

I just had electrical system checked by some battery specialists. They informed me that the alternator that I just had rebuilt last friday is not putting out enough voltage. The rebuild has a warranty but I am contemplating whether or not I should allow them to fix the problem or just buy a rebuilt one from a Mercedes Parts suppliers. What course of action would you all recommend me taking??

Give the original mechaninc and rebuilder a chance to make good. Show them the test results that showed the rebuilt alternator is not functioning and have them propose how they will correct this mistake. That's what a warranty is for, eh? ;)

Then, if they can't get you a satisfactory product, you would be justified in asking for a refund and taking your business elsewhere.

Best Regards,
Jim

Yeah give him another chance. The worst that can happen is it breaks again and you can't play your subwoofers...
MP

they will give him the runarounds again and blame it on the battery and quantum physics etc.Depending on how much you value your time and the **** you are getting ,do what you feel comfortable.
Pay for a reliable rebuilt or pursue for refund knowing you'll spend a lot of time with them

I have often considered these warranties a situation of "If you bring us your car and we break it, we will be happy to break it again for no additional charge". Not such a bargain. I think this idea was stated in "Zen and the art of motorcycle maintenance" but it has been a long time...

I'd take it back myself. I usually get some bs like petaling said, but it's worth a try.
I've been amazed at the balls of some companies. I'll be standing there with a fubar part, a reciept, a box that says guaranteed for life, and they say sorry.

Well I have just ordered a remanufactured Bosch alternator from a reputable Mercedes parts supplier. And this unit is 70 amps, which is a marginal improvement, but it ended up being less than the 65 amp unit anyway. I don't think that I want to deal with the alternator shop again until I get my replacement installed. Then I do not have to work around their schedule. I will give them a chance to fix their work and hopefully will be able to do something with it. Thanks everybody for your help, I don't know where I would have been without this forum. :D I will let you all know when I get the replacement installed, should be by wednesday. Hopefully this will resolve my charging woes!!

Good luck, hope it fixes it.

Btw, that's not woes. Woes was me 6 years ago driving a beemer with a dead alt. For weeks I had to drive to work with a 500W Honda generator buzzin away in the trunk!!

Does operating temperature affect alternator output?? I installed a Stinger Digital Voltmeter I ordered a few days ago, and the readings I am getting from it are puzzling me. When I first turn the car on, meter reads between 12.2-12.6 at idle and rises to about 12.8 under accelartion. After the car warms up, approximately 7-10 minutes later, voltmeter rises and holds around 14.3-14.5, even at idle. But if I turn the car off and start it back up, it drops down to 12.2-12.6 again! :confused:

Hmmm. I could give some semi-educated theories, but I think it's easier to just say I think you're ok. That is unless you really just gotta know. I'm that way myself.

I have a very informative PDF book on how alternators work. If you want it give me an email addy to send it to. It's 3.5M in size.

Upgraded alternator to a Bosch AL129X, newly remanufactured by Bosch. 115 amps hopefully will solve my problems.