Not one of my better P-car days (Alternator failure?)

[scottb]

So there I was, with about 10 other cars zipping down the 210 freeway for Big Bear Run III. Life is good, the car is running great, and I'm in some fast company. Suddenly, I realize the radio has shut off. Then, I step on the gas and get virtually no power. Uh oh. So, I get off at the next exit and roll to the stop light. The car is running, but barely. I step on the gas, and it doesn't have enough power to move. So, I shut it down and look in the engine compartment. Thankfully, the alternator belt is still intact, so the engine didn't cook. I tried to restart the engine, and I don't get even a peep from the starter. It's as dead as the proverbial doornail. My buddy Bob (Bob's Flat-Six on the board), came back and helped me push the car over to the side of the road. (When I was driving, I did notice that the headlights looked dim, but I chalked that up to needing/wanting a set of H4s. I did not notice if the tach was bouncing, nor did I notice if the alternator light came on.)

A flatbed and $200 later, I get the car home. I checked the voltage, and the battery is showing 3.4 volts. (Not 13.4). No sign of battery leakage.

My take is that the alternator has gone belly-up. Anyone have any thoughts on this?

Comments and/or help would be appreciated. Thanks, guys.

[North Coast Cab]

Diagnosis sounds right on. Charge up the battery and start the car. This will answer your question. Assuming it starts and runs it's definitely the alternator. Rebuild isn't too bad, and I've seen some used ones in the classified section pretty cheap also. Good luck.

JG

[mossy97]

Ok, Let's change the scenerio to my little gremlin... I have a 79 911 SC in what I consider to be preety excellent/daily driving condition. When it is raining and I drive with the headlights on, the radio (A/D/S Amp & 8" Nakamichi Subs, Etc.) shuts off and if I stop, I am DOA. If I get a jump start, I can go on and not have trouble again for days/weeks.... I am soooo confused, unless it's the alternater starting to crap out??

Alex

[304065]

It's all about the light. The light is your friend.

If the alternator is putting out voltage, the light will be dark. If the light is partially lit, that means that the battery is putting out more juice than the alternator. The intensity of the light tells you how much current is flowing, and how weak the alternator feedback current is relative to the battery.

If you load the system with lights or a big honkin' amp, you may be getting sufficient voltage but not enough current. In that situation, you may have fried one of the diodes in the alternator.

The best way to test this is with a voltmeter when the engine is running, measured at the battery terminals. Charge up the battery for two days, yes, two days nonstop, on a low (2A) setting. If you haven't gone to a glass-mat type, make sure you have water and electrolyte, measure the specific gravity of the battery electolye with one of those floating ball hydrometers if you must. Ok, now you have 12v coming from the battery. Start the car. If you have less than about 13.8 volts measured on the battery itself, you should verify that your battery terminals are not corroded-- the corrosion can cause a voltage drop. Still not 13.8 or higher? Bad alternator. Disconnect battery, remove coil (early car with coil on fan shroud) remove strap, carefully remove bolts for airguide, unbolt alternator wires. Make detailed notes of what wire goes to what terminal on the alternator to avoid looking like newbie with question to pelican board. (Or use archives!) Take the alt. down to your FLAPS and have them spin it up and check the diode output. That should do it.

Good luck! Plenty of alternator threads on this board, you should find answers to pretty much every question there is.

(I am at the point where I can do an alternator change in 30 minutes. Now I just gotta get it so I don't HAVE to. . . )

[Bob's Flat-Six]

Hey Scott
Good you made in OK, let me know if you need any help.

[scottb]

Bob: I can't tell you how much I appreciate you coming back to rescue me. It was good to know I had a "lifeline." Also, thanks for having Dave give me a call. He thinks it's an alernator, too. I'm going to try to get mine rebuilt locally. I think there are a couple of places in Van Nuys that can do it.

You're a good man, Mr. Flat-Six!