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Voltage output from alternator

Dave400

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I'm currently trying to determine if my 2006 2.2 Ex ictdis alterrnator is failing to provide adequate charge or if the smart charge system is not doing what it should..

If it's not working properly I'll replace it, but if it is then I only need change the pulley or bearing as my car still has the longer polybelt (got the noisy bearing sound that seems common to the usage of the longer poly belt)

My question to you lot is:

At idle I read on a multimeter attached to the cig lighter socket 12.5v. Under load, with lights on, air con on, virtually anything else I can think of on, I only get 11.5v.

The noisy bearing/pulley sound started Thursday evening, the car was sluggish to start Friday evening, didn't touch her Saturday, and Sunday morning she failed to strart (rapidfire clicking)

Can any of you lot confirm what voltage reading you all get at idle and at 2500rpm?

Thanks in advance
 

Stevearcade

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Maybe it's different for the petrol, but I get almost 14 volt.
 

93 accord

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Was a thread on this resently, on phone so can't find link to post up, but basically, engine on, then pull the negitive of the battery, if the engine stops the alternator is gone, if nothing happens, its working. This wont tell you how efficient the alternator is, just is it doing the minimum without the need for battery ***istance.
 

Jon_G

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Was a thread on this resently, on phone so can't find link to post up, but basically, engine on, then pull the negitive of the battery, if the engine stops the alternator is gone, if nothing happens, its working. This wont tell you how efficient the alternator is, just is it doing the minimum without the need for battery ***istance.
I think you're right that a recent thread here suggested this. However, my initial feeling about this is that it's a bad idea, as you remove the major load and 'spike buffer' from the alternator when doing this. So I've just had a quick google on doing this, and all the sites I find advise against this, for example...
http://www.familyhandyman.com/automotive/how-to-test-an-alternator/view-all
http://www.cruisersforum.com/forums/f14/disconnect-alternator-while-running-72507.html
http://www.troubleshooters.com/dont_disconnect_battery.htm
http://uk.answers.yahoo.com/question/index?qid=20090910140229AAJlBOm
In fact, no results for my search approved of disconnecting the battery with the engine running! I guess you might find a site the does suggest this, but (as an electronics engineer) I would strongly suggest you don't do this.

Measuring the voltage across the battery terminals will safely tell you all you need to know... voltage should stay up at 14v or more with the engine running at 1500 RPM if the alternator is working OK.
 

93 accord

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It helped the last person on the previous thread on a 7th gen. Race cars dont run batterys and have quick release and connections for batterys and there is no problem, they do this every time they start up. And yes they do have canbus systems in place still etc. I give this option over the simple multimeter test because some members may not have a multimeter to hand thats all ;) Also if your battery is a major load, then the battery is gone too, hole in bucket scenario :lol:
 
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