checking alternator output

[monsterdog]

Is there a simple way to check the alternator output with the engine running on a 944 turbo without a) taking off all of the habitrail-like turbo hoses, airbox, air sensor, etc., and b) chewing a hole with a starved circus trained rat through the air hose shroud at the back of the alternator - is it even possible to remove this thing enough to get at the connections or the regulator without taking the whole alternator out of the car? or further mutilating my bleeding knuckles?

Battery isn't charging, and the alternator was just replaced
by a mechanic in Flint, Mi, where I got the car before I drove it 1200
or so miles to Florida with no problem.

About two weeks later, it just goes kaput, so to speak,
and the dash light is constantly on and the battery measures about 9-10 volts when running and 12.6 when the car is off at the main terminals.
Is it possible this thing is fried already?

I noticed that the air hose which runs from the nose to the alternator shroud has been missing, possibly for quite some time or at least for the duration of the drive down. I'm praying that it may just be the regulator. Sometimes the alternator warning light will dim a bit if I race the engine up to 3000 rpm, but the needle still hovers right around 10 volts at the gauge. (I wonder whether the mechanic forgot to put the air hose back in, along with fixing the air box allen head bolt he broke when he was taking out the air box to change the darn thing.)

The connections at the starter seem to be pretty sad and corroded, not sure if this may be a contributing factor. It's difficult to get to them, even with my gumby like build.

I feel like if I took it to the shop down the street he'd just laugh at me.
Alternator? What alternator? I don't see one!

Back to driving the bronco for a while. 0-60mph in about 17 seconds.
Dog loves it, but it scares all the girls and souped up hondas away.

[mike944]

If you're getting 9-10 volts when the car is running, the alternator is definitely not working. Is the belt tightened properly? Maybe it's slipping. That could cause the same symptoms, except you would probably smell burning belt.

If your starter leads are corroded, it's possible other things are as well. Check all your grounds first.

If that leads you nowhere, get a wiring diagram, and you can probably figure out where the wire goes that comes from the alternator. That would be my next test-point. If it's still bad, have fun with the trained circus rat, and try to test the output connection on the alternator itself.

I don't think the regulator is a seperate piece, i'm pretty sure it's part of the alternator, and therefore can't be replaced seperately.

is the alternator new, used, or rebuilt? Used ones are always suspect, and the quality control on rebuilt ones is not always up the ornginal standards. Even a new one can go bad, if you got a "lemon". Warranty?

Here's another thought........ if the air hose is missing, it's possible that the alternator overheated, and something burned out. That hose is there for cooling air to the alternator.

[IceShark]

You can't get to the back of the 951 alternator for the output post without removing all the turbo plumbing. Then you need to put it back together to run the motor and see what the output is.

If your battery actually drops in voltage when the car is running, that alternator isn't working, or at least not very well. You could have a bad voltage regulator (cheap to replace), lost some diodes or a loose alternator belt. Could be some other items but those are the top ones that are likely.

The voltage regulator is quite simple to replace - takes about a minute once the alternator is on a bench. But on a turbo you have to remove the alternator unless you can get a small child with very small hands to work on it for candy.

I'm sort of surprised you drop voltage at the battery from 12.6v at rest to 9 or 10 when the car is running with nothing else on. That is a pretty big drop. The car only takes about 7 amps to run the ECU, KLR, HVAC fan on low, spark, etc. Something else may be going on, hope it isn't a short.

You should be aware that the ECU stops working altogether around 9 + volts so don't go on any trips. Also, not having the vent tube to the front of the air scoop probably didn't matter in killing your alternator. Didn't help any but I doubt it fried it. Remove the plastic heat shield and let the turbo roast the alternator and that is a totally different story.

So I think you need to remove the alternator and bench test it. Then rebuild what is required.

[dmsog]

I rebuild alternators professionally and I must say that for every ten Bosch units I do, I MAY see one bad regulator. This is over a period of 27+ years. If the light is on and fluctuates with rpm you have either a stator or rectifier problem in the alternator. This is usually accompanied by an audible howling noise coming from the alternator.
You can take this to the bank.

Doug

[bearone2]

check to make sure the alternator lite comes on when you turn the key on.

[john dory]

try a meter across the battery terminals with the enginge running, it should read around 14.4 volts

[Granite 944]

Just for grins and giggles.......take your battery out and have it bench tested at your local sears, or auto parts house. It will at least eliminate the possibility of a shorted battery being the problem. Considering the altenator was recently replaced.....thats what I'd look at first.

[dmsog]

Originally posted by Granite 944
Just for grins and giggles.......take your battery out and have it bench tested at your local sears, or auto parts house. It will at least eliminate the possibility of a shorted battery being the problem. Considering the altenator was recently replaced.....thats what I'd look at first.

...that would be a waste of time. Battery condition has nothing to do with the fact that the idiot light is lit.

Doug

[monsterdog]

Well, the verdict is in, battery tested o.k. The alternator, however, is fried. The internal componentry is melted and otherwise kaput, and this is only after 30 or so hours of use. On the bright side, the company which remanufactured the part, Precision Parts out of Oklahoma City, is airmailing a replacement to the closest shop that deals with them in Tampa. A 45 minute drive but worth it for the free exchange. Hopefully the "new" one will outlive the "old" one. After I got the alternator out from the engine compartment and brought it inside to examine the spoils my dog growled and barked at it. Maybe I should let *her* diagnose componentry from now on.

Btw, the local alternator specialist was figuring on ~$150 for a rebuild with a few days to get parts. Car parts stores were chiming in at around ~$200 for a replacement alternator, not sure whether original equipment or not. I didn't bother calling the local Porsche dealership, but they have these really cool keychains...

Thanks for all of your help and knowledge.

[Granite 944]

Originally posted by dmsog
...that would be a waste of time. Battery condition has nothing to do with the fact that the idiot light is lit.

Doug

Really?.........hmmmmm.

Monsterdog, glad to hear your gonna get a free replacement!