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914World.com _ 914World Garage _ new problem: alternator on a 3.6 ...

Posted by: SirAndy Jul 25 2007, 09:52 PM

so the clutch finally works, got it all back together this afternoon, drive home went without a problem.

i pull in and park the car and come back 10 minutes later, start her up and the alternator light stays on ...

rev her up, no change. turn her off and back on, same thing.
i checked all the fuses, rotated them, no change.

now effin what? alternator on a 3.6 is internal. how do i check on it ???
Andy

Posted by: drive-ability Jul 25 2007, 10:00 PM

QUOTE(SirAndy @ Jul 25 2007, 08:52 PM)

rev her up, no change. turn her off and back on, same thing.
i checked all the fuses, rotated them, no change.

now effin what? alternator on a 3.6 is internal. how do i check on it ???

Andy

Andy,
You could start by checking the battery voltage to see if the charging system is exhibiting a problem.

Posted by: Dr. Roger Jul 25 2007, 10:12 PM

this thread may help. the last few postings are the applicable ones.

http://www.dorkiphus.net/porsche/showthread.php?t=7536

sounds like the exact same thing.

Posted by: McMark Jul 25 2007, 10:22 PM

Did you reconnect your ground cable? Just a random thought....

I'm inclined to think it has something to do with that new gauge, but I can't say what.

Posted by: SirAndy Jul 25 2007, 10:27 PM

QUOTE(Dr. Roger @ Jul 25 2007, 08:12 PM)

sounds like the exact same thing.

nope. see, it worked *fine* all the way home. if it was missing an external resistor or diode or whatever, i would have had that problem from the beginning.

i never touched the alternator. lights was off during my drive home.

it wasn't until i restarted the car, that it stayed on.

Andy

Posted by: SirAndy Jul 25 2007, 10:28 PM

QUOTE(McMark @ Jul 25 2007, 08:22 PM)

Did you reconnect your ground cable? Just a random thought....

I'm inclined to think it has something to do with that new gauge, but I can't say what.

yes, ground strap attached ...

i took the old gauge with me. thank god i didn't hack into the harness, switching them out will be easy ...

Andy

Posted by: McMark Jul 25 2007, 10:30 PM

QUOTE(SirAndy @ Jul 25 2007, 08:27 PM)

it worked *fine* all the way home

I debated even posting that because I knew you would say that. But I just gots a feeling. When it's all over we'll see who's right and who's not.

Posted by: PRS914-6 Jul 26 2007, 01:00 AM

Andy, it looks like you just installed new gauges. Yes? The alternator light MUST work since that circuit is what excites the alternator. So if the alternator light is not making a circuit, or the bulb is burnt out or not hooked up, that is your problem.

Good luck.....

Posted by: SirAndy Jul 26 2007, 01:28 AM

QUOTE(PRS914-6 @ Jul 25 2007, 11:00 PM)

So if the alternator light is not making a circuit, or the bulb is burnt out or not hooked up, that is your problem.

yes. i know. like i said, the light STAYS on. doesn't go out. meaning, the bulb works ...

see, lighty worky ...

IPB Image

Andy

Posted by: John Jul 26 2007, 10:50 AM

You did check your belt(s)?

Posted by: McMark Jul 26 2007, 11:01 AM

Did you check the battery voltage running and off to see if there is a difference?

Posted by: dakotaewing Jul 26 2007, 12:23 PM

Another blury pic by the artist known as "SirAndy"....

Posted by: SirAndy Jul 26 2007, 01:56 PM

QUOTE(John @ Jul 26 2007, 08:50 AM)

You did check your belt(s)?

belt(s) are fine ...

QUOTE(dakotaewing @ Jul 26 2007, 10:23 AM)

Another blury pic by the artist know as "SirAndy"....

hey, i've got a reputation to uphold ...

QUOTE(McMark @ Jul 26 2007, 09:01 AM)

Did you check the battery voltage running and off to see if there is a difference?

here are the numbers, across the battery terminals:

• 12.61 V - ignition off
• 12.38 V - ignition on
• 12.06 V - idle
• 12.08 V - idle with gauge bulb disconnected, just for the giggles ...

clearly, it's *not* charging ...

Andy

Posted by: McMark Jul 26 2007, 01:58 PM

I don't remember, is the stock diode hooked up to anything?

Posted by: SirAndy Jul 26 2007, 02:03 PM

QUOTE(McMark @ Jul 26 2007, 11:58 AM)

I don't remember, is the stock diode hooked up to anything?

yes, stock diode is hooked up, but it's not for the alternator circuit. it's for the brake circuit.
it's used because the brake warning light has multiple functions (parking brake, master cylinder, seatbelt interlock and emergency flasher) ...

Andy

PS: to clarify, there's a diode in the alternator circuit on early cars, but i have a '74 main harness ...

Posted by: Marty Yeoman Jul 26 2007, 02:08 PM

Can, or did, you check the voltage regulator?

Posted by: SirAndy Jul 26 2007, 02:09 PM

QUOTE(Marty Yeoman @ Jul 26 2007, 12:08 PM)

Can, or did, you check the voltage regulator?

i wouldn't know how, it's all internal ...

Andy

Posted by: SirAndy Jul 26 2007, 02:14 PM

alright, i need some strong coffee. i'm gonna drive her up to starbucks (about a mile from my house) and see what happens ...

got my AAA card with me ...
popcorn[1].gif Andy

Posted by: Dr. Roger Jul 26 2007, 03:00 PM

My internally switched alternator has but one wire connected to it.

It is tickled by low voltage from the thick wire coming from the battery.

Does yours use 1 thick wire or are there 2 or more wires?

What model and year is your engine?

Posted by: SirAndy Jul 26 2007, 03:26 PM

QUOTE(Dr. Roger @ Jul 26 2007, 01:00 PM)

My internally switched alternator has but one wire connected to it.
It is tickled by low voltage from the thick wire coming from the battery.
Does yours use 1 thick wire or are there 2 or more wires?
What model and year is your engine?

i'll have to take the shroud off the motor to get a look.
there's no easy access to the alternator.

'95 993 3.6L motor ...

Andy

PS: leaving for starbucks, be back in a minute ...

Posted by: McMark Jul 26 2007, 04:04 PM

Uh oh, it's been 30 minutes.

Posted by: SirAndy Jul 26 2007, 04:33 PM

yeah, yeah ...

now, riddle me this:

after i got to starbucks and gulped down a double shotted espresso, i walk back to the car and fired her up.
light stays on, like before. parking lot is empty, so i give it a "spirited" takeoff.

and the damm light goes OUT !@*!!

so i pull over and put the multimeter to the terminals:

• 12.95 V at idle
• 14.04 V at 3k rpm

now it's working again ?!?

i suspect i either have a lose connection somewhere or the voltage regulator is on it's way out the door ...
Andy

Posted by: John Jul 26 2007, 04:33 PM

QUOTE(SirAndy @ Jul 26 2007, 01:26 PM)

QUOTE(Dr. Roger @ Jul 26 2007, 01:00 PM)

My internally switched alternator has but one wire connected to it.
It is tickled by low voltage from the thick wire coming from the battery.
Does yours use 1 thick wire or are there 2 or more wires?
What model and year is your engine?

i'll have to take the shroud off the motor to get a look.
there's no easy access to the alternator.

'95 993 3.6L motor ...

Andy

PS: leaving for starbucks, be back in a minute ...

That's one of those jobs I would pull the motor for....... Like the clutch.....

Posted by: McMark Jul 26 2007, 04:49 PM

I seem to recall that a bad battery might cause this....

Posted by: SirAndy Jul 26 2007, 04:57 PM

QUOTE(McMark @ Jul 26 2007, 02:49 PM)

I seem to recall that a bad battery might cause this....

hmmmmm, it's 4 years old or so ...

maybe i should swing by flaps and get a new one ...

Andy

Posted by: geniusanthony Jul 26 2007, 05:32 PM

In the interest of helping someone else out, I will admit my brain lapse with my -4's charging system.

After going through two new Optima redtops and swapping my OE alternator for a new one(which sucked) It took me a solid day of lookin and head scratching till I plugged the alternator lead back into the relay board. and Low and Behold she lived.
I feel much better with that off my chest by the way.

Posted by: drive-ability Jul 26 2007, 09:50 PM

Andy,
Before I dug in and removed anything I would just do some manipulation of the harness in the engine bay and any other related areas. Clearly its possible theres a skew some where that may show up. I would do it with the engine running so you can see any changes on the fly. Maybe have someone with there eyes on the dash or a dvom. I don't see hammering the throttle shaking loose an internal alternator problem but surely a wiring issue.. would be effected by vibration and engine twist.