David0514

The alternator light came on in my car. It is only on when the car is off (Key in off position or not in at all). Is this a sign of a bad alternator or a bad voltage regulator. I have read both in two different places. I had the alternator replaced 475 miles ago. I have had to charge the battery numerous times and usually have power problems after leaving the parking lights on for an extended period (20 mins)without engine running (fixing lights). Problem being car won't turn over until I recharge battery. Battery I replaced with alternator back in April.

Thanks in advance.

Adrian

What model 911 are we talking here David. The warn light only comes on when the alternator output is zero and when the engine is running. I have no idea how this can occur without power applied. I do not know your model and the elctrical diagrams for this model would be required to try and work this out.
However from the problem you have described I would say that either the alternator brushes are gone or the regulator has gone west. Again the model is important because are we talking combined alternator and regulator assembly or earlier model separate units.
Dead battery like this means it is not being charged. It has no capacity. It is very common to purchase rebuilt combined alternator/regulator assemblies only to find that the regulator has not been rebuilt.
Ciao,
Adrian
911C4

PS: Does the battery return to a full charge when you recharge it. I wonder if you have a nice short circuit somewhere between the battery and the alternator. The battery is hard wired to the alternator. A short in the alternator may bring the light on even though power is not applied.

Jamey

Here ya go David.
Author Topic: Help!!...Need an electrical Guru
Jamey
Member posted 04-28-2001 01:44 PM
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I'm hoping someone will have some insight to my problem. I have an '82 SC used as a daily driver. Today after a short drive I noticed the battery light stayed on with the ignition off and with the key removed. I disconnected the battery, inspected connections, then hooked it back up. The light still came on. Goes out when car is running though. Weird!! I pulled the guage but all connections there appear to be okay. Starting power seems fine so I doubt it really is a low battery. I hate to say it but I can't find the alternator on my car. Jiggling key switch didn't help either. Any thoughts guys?
Jamey
'82SC
'84 928S

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83 sc euro cab
Member posted 04-28-2001 01:54 PM
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try adding aother light bulb in there and see if the problem persists. also check that everything else electrical is turned off when you turn the car off...
there shouldnt be any flow of electricity (maybe except to the clock) when you shut off your car



oldE
Member posted 04-28-2001 02:34 PM
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Jamey
I would guess the electrical contacts inside your ignition switch are not opening again when you turn off the key. Try another switch if you can.
Les

john walker's workshop
Member posted 04-28-2001 04:08 PM
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your alternator is the culprit. a diode problem, feeding power back to the light. have you hooked up jumper cables backwards lately?

Jamey
Member posted 04-28-2001 04:34 PM
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No I haven't jumped the car at all. No new electricals added either. The CD player did start having a few problems about 3 days ago(cd's wouldn't play unless I ejected them and then reinserted). Would the diode allow current back to the light even with the engine off/key off and removed?

Jamey
Member posted 04-28-2001 05:12 PM
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Well I just went out and started the car. When I disconnected the positive battery cable the engine immediately died. So, unfortunately, I think John Walker is right in saying my alternator is bad. Darn, I was getting my front seats reupholstered next week!! That may get put off now.

911pcars
Member posted 04-28-2001 05:17 PM
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If your alternator's wasn't dead, disconnecting the positve battery cable while the engine was running probably did it. Next time, don't do it.
Sherwood Lee http://members.rennlist.org/911pcars


Wayne at Pelican Parts
Administrator posted 04-28-2001 05:29 PM
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Yup, alternator is having problems. Here's a table from one of the tech articles on the site:
The following guidelines are useful for troubleshooting your alternator:

Alternator indicator lamp is on with the ignition key off.
· Alternator has failed, and diodes have shorted out. Replace alternator and in the meantime, disconnect battery to prevent it from becoming completely drained.

Alternator indicator lamp does not light when ignition key is turned on.
· Alternator bulb has burned out.
· Regulator has failed
· DF wire is disconnected or broken from alternator
· Alternator has failed, and internal windings are open

Indicator lamp remains on after engine is started and running above 2000 rpm
· Regulator has failed
· Battery lead to alternator has been disconnected
· Alternator is not firmly grounded
· Alternator internal bushings are dirty or worn
· Alternator is bad

Indicator lamp is dim after starting, and gets brighter as engine rpm increases.
· Battery lead to alternator loose or bad
· Ground connections are bad
· Battery is bad
· Alternator is bad due to open diode failure

Indicator lamp is dim after startup, but eventually gets dimmer and goes out when engine RPM increase.
· Low charged battery
· Poor connections to battery

Indicator lamp is dim after startup, and gets dimmer as rpm increases, but never goes out.
· Regulator has failed
· Alternator is failing

Jamey
'82 911SC

David0514

Thanks all for your reply. My car is a 77 Carrera (WOR) car with 3.0L. Would the voltage regulator be inside the alternator or outside on the engine compartment wall(left side)? Also, I had the alternator replaced by a shop 475 miles ago.

Someone was asking, the alternator is buried behind the fan somewhere. You can not see it without removing somethings.

Thanks again all.

H.B.

Hi,

After reading Jamey's post I'm starting to wonder if my problem is related to the alternator/regulator or the battery. The headlights seem dim and their intensity varies with the engine speed, but the alternator light is intermittent and goes off when the engine speed rises above 2000rpm suggesting (according to his post) a battery problem. The only other thing I should mention is the fact that seatbelt light started coming on randomly when I first noticed this problem; and I was told this could indicate a bad voltage regulator. I understand that it's best to have the system tested, but I was hoping someone might be able to pinpoint the problem beforehand.

Thanks

Jamey

HB, the first thing I would do is get out the digital voltometer. Check voltage at battery terminals with engine off. Should be aroun 12.5V. Then check it with engine running.It should have increased to around 13.5 at idle. Just analyze the 2 numbers to determine if it's a battery failing to accept a charge or alternator just not charging.
Goodluck.
Jamey www.geocities.com/jamey928/index.html