I'm trying to figure out if my alternator is working properly. I followed the instructions in the tech ref. files on changing to a newer internal regulator type on my '71 chevelle. I'm confident it's wired up correctly. It seems that my battery goes dead every so often. Is there a way I can tell if this is from a malfunctioning alternator or from some other source? I will pull the alternator off and have it tested though. I guess my main question is how long will a 406 small block with a 50,000 volt HEI run on JUST the battery - assuming the alternator wasn't working?

Thanks!

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1971 Chevelle Malibu - 406 sbc TH350

Pictures of my '71 before I got it home (http://www.adam_nova.homestead.com/Untitled1.html)
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I don't know how long the car will run, but in a pinch (no volt or amp meter), you can start the car, and with it idling, disconect the battery (negative cable safer?). If the alternator isn't working, the car will die immediately.

But this won't diagnose a weak alternator, only a "dead" one...

I have heard this is not too good for the alternator (thats why I said,"in apinch" when you don't have other options...), but I have used it many many times...

[This message has been edited by 1966_L78 (edited 05-11-2001).]

Never ever do that! Not even in a pinch! People are under the illusion that this is a "test", the answer is NO. With "no" battery gives the illusion of a completely dead battery--the alternator will try to go full field and strain the **** out of itself. If the thing doesn't get ruined, you've shortened it's internal components working life.

Get a voltmeter! With the engine idling (about 1000 rpm's) take the voltmeter probes and touch them to the batter terminals. You should read between 13.8 and 14.2 volts ideally---this means charging system is working. Above 14.5 volts is too hi in my opinion. Below 13.8 volts means any extra accessories are really going to bog down the system when they are turned on.



[This message has been edited by Coppertop (edited 05-11-2001).]

Coppertop, what about this... My car will start instantly, no problem. The Autometer volt guage will read 12volts exactly. Driving around at various rpm's and the guage may go alittle above but sometimes below 12(scary). Then I'll shut the car off, refire it and I've got 14+ volts. What's going on here? It's a new 140amp alternator. Did I somehow damage the exiter inside it?

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70 Chevelle SS396/TH400/3.73 "What does not kill me, makes me stronger."

Coppertop,thank you thank you thank you!!! I've almost gotten into fist fights with people about the "pull the negative cable" deal. The ones I like the best are the ones with a 95 something or other and when I tell them they could damage their ECM they say "I do it all the time!" like they're Mr. Goodwrench or something. Sorry to interupt but I wanted to get that out.