benjr

i recently removed my alternator and replaced it with a Bosch rebuilt from autohaus az. I decided to have the fan shroud powder coated in the process. After I reinstall everything the alternator is charging and everything checks out fine. Except the fan blade is scraping slightly. The shop I went to had done this before and had examples of their work. I also replaced the fan. After a month the car kept dying due to the charging system. The battery is about a year old but it holds a charge. I tested both batt and alternator with a voltage load tester

Would a slightly loose alternator belt cause this ?

I would think the Bosch rebuilt would last.

Any input would be helpful.

???

mgianzero

Ben,

We'd love to help, but there's too much unknown here.

Here's just a few questions that can help us lead to the source of your problem.

1) What voltage did you read and where did you measure it? (at the battery or someplace else) Remember, a strong alternator (which yours should be since it was rebuilt) should read over 14 volts with engine idling (minimal load - no lights or radio). And a dead battery is anything less than 12 volts.

2) Have you measured your standby current drain with everything off? (ignition off, all lights - dome, glove, luggage and engine compartment off). This should be less than 30 mamps.

3) How did you determine the tension on your V-belts? V-belts are somewhat subjective to exact tension when assessed by different installers. However, a belt tension tool gauge, such as the Porsche krickit, is a great one to have in your car. They're cheap and quite easy to use. I believe Porsche recommends 30-40kPa on their belts, but you should look this up to be certain. Also, after about 500-1000 miles of stretching the new belts, you should recheck the tension - they often loosen up initially.

4) A slipping alternator belt can screech when it slips (especially under load). Do you hear anything? Are you using Porsche belts or some aftermarket? The consensus here is to use only Porsche.

benjr

I used a battery load alternator starter tester from harbor freight. The voltage was 12.6 volts with the engine off. After starting it the voltage drops to bellow 12 volts. Battery load test ok. Alternator test fail. I used new porsche belts and used the same # of shims. It has more slack than the fan pulley. I bought a gates version but it wasn't sensitive enough and too big. It's only slipped a few times on start up not while driving. I'm usually pretty good judging tension by feel. In the old days we tuned cars by ear.

mgianzero

Wow, alternator should be AT LEAST pulling 13.5V if it's healthy. A drain, short, or bad ground can certainly effect these numbers.

Before you say the rebuilt alternator is no good, I would check that your grounds are good. Test the alternator at a location closer to the source (the alternator). You "may" read different voltage drops when your grounds are not true. (I think you can hook something up to measure inside the engine fuse box.)

Also, I would also test to verify you have no drain on the car. That's a quick and easy test with an amp meter at the negative battery strap. That would effect everything.

I would think it's unusual for a rebuilt alt to fail like this, but it's not unheard of. Bosch also does not hold the same reputation that they used to.

I know there are other experts who can chime in too --- Alex, where are you bud?

Marc

justin-in-athens

The alternator itself may be ok, but you may have a bad voltage regulator. This device basically signals the alternator to charge the battery, if it were not functional, the alternator would never charge the battery.

You could try just replacing the VR, but its a lot or work to pull it and replace. http://www.ebay.com/itm/BOSCH-VOLTAG...15766a&vxp=mtr

mgianzero

Yes, that is a possibility, but wouldn't it have been replaced when rebuilt? I figure, if you're going to go this far, pulling the alternator out, then you might as well bring it to a shop to test it. I was trying to avoid doing this unless the more simple tests come back normal.

benjr

The rebuilt alternator included a voltage regulator. It's a Bosch rebuilt from Autohaus AZ. The battery holds a charge. I do have a amplifier for my stereo. I'm wondering if that fried my voltage regulator? The original alternator has lasted 14 yrs 60 k miles so I assumed replacing with a rebuilt Bosch would do the trick. I completely disconnecyed the amp and the issue still persists. My last step before pulling the alternator is to check the cable between the alternator and the battery. Is this the main battery cable or the smaller wire attached on the right side of the batt terminal? Does the charging wire harness fail? This sounds pretty labor intensive. The ring terminal doesn't appear corroded. How do I test for a corroded cable between the alternator and the battery?

mgianzero

Yes Ben, that's what I assumed - new voltage regulator comes with a rebuilt alternator. I might be mistaken but I don't believe a bad amp can blow the voltage regulator though. Some electrical engineers might have some further input on this.

The alternator should have a direct positive line that comes straight off the battery. The smaller wire is probably for your amplifier. Try disconnecting there to see if amp goes out and if you get any better voltage differential than just 13 volts at battery with car idling and no draw. Also check your ground strap off battery - bolts to frame. Disconnect and clean it. There should also be a ground in back of car for alternator (not sure where that is) but check that too if you have easy access to it.

Did you check your circuit for a current drain? That's an easy test. Just disconnect battery at ground strap and connect your multimeter in line b/w battery negative ground post and battery ground strap. Make sure your multimeter is set up to measure the correct amperage though. If you don't, you can blow the multimeter fuse and then you'll read zero. You then have to replace the fuse (common part at local hardware store / Radio Shack).

benjr

I went to do the drain test but the battery was dead. Charging the battery now. I removed the alternator wires from the battery. Wires seem to be in good shape no corrosion. Same with the negative ground on the body. The connection on the body is corrosion free. Looks brand new. I attached a pic. I noticed that the last time I started it that the battery light on the dash was on and remained on even after I turned the car off. I left the car locked up and the battery light remained on until the battery died. Once the battery is charged I will post the results of the drain test.

NP993

The "rebuilt" alternators don't have a great track record. The one I bought a few years ago lasted 10K miles before crapping out. Don't be shocked if yours is bad....

mgianzero

Noah has a good point. You can never trust a rebuilt component unless you know the person doing the labor. I've known rebuilt starters that crap out prematurely. Let's hope it doesn't come down to that.

Jay J

If any of you need a good place to test or rebuild your Alternator take it to Rotex in Gardena; the owner there was explaining to me how Bosch units usually run on the lower side of power from the Get go

Davies

If it's original, I'd replace the negative battery wire. (battery to frame). Forget how it "looks", just replace it for 15 bucks so it can be eliminated as the cause. They do go bad/lose conductivity over the decades and cause all sorts of truly weird electrical trouble. I've been there.

GC96

I would agree with this. I had some weird electrical issues about a year ago and it turned out to be the battery ground strap. I initially thought the ground strap was fine because it looked good. However after replacing a couple of other components that didn't fix the problem I noticed that the resistance measurement across the ground strap was higher than it should be. I removed it and found that there was actually corrosion inside the crimp connector that couldn't be seen when the wire was installed. Mine was the original cable which was a bare wire similar to your picture. The new replacement ones have an insulating sheathing along the full length and do a better job of sealing the crimped connections.

GC

benjr

Thanks everyone I will replace the ground strap. Makes sense. Battery has always lost charge over time. The battery has been disconnected from the car and there has been a voltmeter on it for 4 days. So far no voltage drop. In case I need to troubleshoot the + wiring to the alternator can someone comment on the attached image wiring diagram. On the battery terminal there are 2 4 gauge cables. I assume one goes to the fuse box and one to the charging starter system. The diagram looks like one + cable goes from batt to starter then to the alternator. Wondering if the issue could be at the starter connections if the ground strap doesn't fix it.