Alternator to battery testing question

[nborton]

Is this a valid test to warrant replacing the wire from the + alternator to the + battery:

With the car running, the alternator + to battery + reads 13.4. With everything connected and the car running, placing a voltmeter between the alternator + and battery + reads 0.5V. Should this read 0? and if this is a measure of the voltage drop across the wire, .5V seems high.

Is this logic right?

 

[gmcturbo]

Re: Alternator to battery testing question

yes, you are measuring voltage drop across that wire. 500mV seems a little high i wouldn't replace the wire though. how about just cleaning/tightening the connections?

i looked this up for ya- the wire should have 500mV drop maximum.

 

[ircwet]

Re: Alternator to battery testing question

how long is the wire.....it will have resistance....

 

[Don W.]

Re: Alternator to battery testing question

Is this a valid test to warrant replacing the wire from the + alternator to the + battery:

With the car running, the alternator + to battery + reads 13.4. With everything connected and the car running, placing a voltmeter between the alternator + and battery + reads 0.5V. Should this read 0? and if this is a measure of the voltage drop across the wire, .5V seems high.

Is this logic right?

It is a valid test. If I read you correct with the alt DISCONNECTED you have 13.4 and with it CONNECTED you have 0.5 However I almost don't believe it. If, in fact, you are placing a voltmeter from the alt output to the bat + term, with everything CONNECTED you should get a a reading of nearly -0-. My truck showed 0.02 volts. If I read you correct AND If what you say is correct you've got a rather bad connection somewhere, or the wire itself but connections first as mentioned.