Altenator Died No Warning Light....

[jabb]

Just back from a weekend in Vermont with a PCA tour. Unfortunately it was a rainy weekend and my altenator died the worst part is that the warning light never indicated a failure ??.

We arrived Friday night and the 160 mile drive up is fine. Check in to the hotel get back in the car start it up and I notice a slight flicker from the altenator warning light last about 2-3 seconds just flickering. This happens 2 more times that night. Next morning up early down to the local garage load test the battery looks good altenator charging a bit High 14.2...

I figure well at least it is charging...
Go on the tour appox 165 mile tour through Vemont... Coming back to town about 10 miles from the Hotel and the car dies... Oh no...
I know what this is. Some one has one of those jumper/Battery packs with them put it on the car and drive back into town off the battery pack. Back to the garage charge up the battery load test bettery is good but Altenator is not charging.

No way is this guy touching my car... we put a full charge on the battery last night and off we go this AM. Dorve about 1hour and 20 min on that battery pulled into a rest stop
and switched batteries with another PCA member. My battery still had enough juice to start his car. But figure this is a safer place to switch then on the side of the Road. Drove off his battery about another 1 Hour 1/2 home. BTW the car is an 84 with Electric Fuel pump and EFI used no other accesories and got pretty far just off the Battery.

My question is why no Warning light now that the Altenator is not charging. Just a couple of flickers in the begining when it was slightly over charging ? Is it worth putting in an Amp gauge to get a more accurate reading from the Altenator. Where
would I splice one into the circuit.

Sorry for the long Post...

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• Joe A.
• 84 911 Targa
• 75 914/6 3.0

[Automahn]

Just use a digital voltmeter on the battery it will tell you how many volts it is putting out when the car is running.

[Early_S_Man]

Flickering warning lamp can be a sign the brushes are going out ... and when they do finally go out, the circuit for energizing current is open, and no lamp, since the lamp is the source of the energizing circuit!

No, an Ammeter is not worth the trouble! And, anything from 13.5 Volts to 14.5 Volts is acceptable ... besides, meters do vary in accuracy!

A $20 in-dash digital panel meter is more valuable, and very easy to wire into the system! The big problem is deciding where to mount and install it ... how about the console, isn't there a gap between it and the bottom of the dash? Filler panel, suitably covered in black vinyl might be easy enough to do.
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Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 06-03-2001).]

[Jens Wendorff]

Alternator light usually means, that there is an electric flow between the alternator and the battery which is out of spec.
It does not need to be a bad alternator.
I had the situation once, that the light was coming on AFTER I shut down the engine and left the car (keys in my hand!!!). I just noticed by chance as I parked the car in a very dark corner of a public garage (no P-car).
Turned out to be a bad insulation of a wire to the alternator, making a short, and leading to a flat battery. Contact only happened when the engine was cooling down.

Just another hint...
Jens

[jabb]

Thanks for the Input guys I will be taking it apart in the next day or so and will pay special attention to the connections.

Where would be a good spot to splice in a digital Amp Gauge. Could I grab it from the hot lead to the Cigaraette Lighter ??

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• Joe A.
• 84 911 Targa
• 75 914/6 3.0

[john walker's workshop]

you need a volt gauge, not an amp gauge. an amp gauge would have to be inline with the big red wire from the alternator to the starter. a potential wiring disaster if anything shorts out. a volt gauge can be tapped into any 12V source.

[This message has been edited by john walker's workshop (edited 06-05-2001).]

[Jens Wendorff]

John is again right:

When I purchased my car, I had a fire in the cabin on my way home (stopped smiling immediately). I pulled to the right on an autobahn exit which is not much fun.
Turned out to be a bad Amperemeter, wired (correctly)between the alternator and the battery. Well, after 15 or 20 years, it just broke leaving a short behind.
Took me a couple of weeks to figure out later why my car was running on batteries only.

This may be an addition to the topic about the charging light as well...

Jens

[Roy M]

Symptoms are the same as happened to mine. Connection from starter motor to alternator had failed at starter motor end - may save you some strip down time (flickering was, I assume, and intermittent connection due to wire hanging next to terminal). If your light doesn't come on when the ignition is switched on then it is either the alternator (when the above advice applies) or a connection from alternator to charging circuit.

Roy

[joehahn]

My alternator lamp has never come on ever. I bought car with it inoperable and frankly didn't really care but it would be nice to know what is going on. Can I just install the volt gauge that Warren wrote about above in lieu of the lamp? Sounds like that may be easiest? Is there a simple way to determine why my indicator isn't working? Presumably if I supply current and ground to the unit somehow, the bulb should at least light and tell me it is not bulb right??? Any ideas to trace problem?

[Jens Wendorff]

I would check in the following order:
1) Check bulb (use a 9V battery, e.g. of your ohmmmeter)
2) Check socket
a)use 9V battery with a free wire to splice into the +connection
b) Check ground connection with an ohmmeter.
b1)between socket and instrument (push socket in half way and measure)
b2) between socket/instrument and chassis

3) Now its getting complicated: Check wiring diagram for the alternator light. There should be one or two connections in your car, e.g. the 14-pin connector in the engine compartment
-Anyone with more details on this?-
4) If all this fails, pull your alternator and check connection between alternator and 1st connector in the line (both before and behind!).
5) Now you have pulled your alternator anyway-so bring it to a shop for checking and/or rebuild

Usually you should figure out the problem up to step 3).

Good luck,

Jens.

P.S.: Your alternator light is your only warranty that the engine fan is blowing and your engine will not overheat and explode!!!!!!!!!!!!!!!!!!!!

[Jorgeman]

jabb--a burned out bulb will keep the alternator field from being energized and consequently there'll be no output. I checked the Bentley manual and I quote "....on some models of Porsche cars a burned out instrument cluster alternator warning light
will prevent the alternator from charging."
You MAY just be a bulb replacement away from
happiness!!

George 86T

[Joe Bob]

I had the same problem coming back from AZ race weekend...no warning, no light...loss of power and was able to limp into Palm Springs. Was able to get a rebuilt from Lighthill Porsche Repair.

Had to spend the night....gotta have a better way to anticipate failures....

Next on my to do list is a gauge....

[machintek]

FYI. An ampmeter is really a calibrated voltmeter that measures the voltage drop across a known resistance called a shunt. This usually has a low resistance value as it puts a burden on the circuit and also creates heat. The ideal solution would be to move the shunt out of the gauge itself and put it as close as possible to the battery. I personally believe that an expanded scale voltmeter will tell you a lot more as you only need to see from 11 to 15 volts. that should tell you all you need to know.

George
83 911SC Cab/euro/US Marshal auction