testing alternator

[Guinness]

Right well im a bit nackerd with the alternator lark and have swapped to a new alternator. Can anyone tell me how test the alternator at the alternator using a multimeter. I need to identify if its a cable or if its the new alternator. The new alternator if anything is worse, so Im thinking either another duff alternator or a loose intermitent wire.

Any input much appreciated. Doubt its much good checking the battery at the battery side.

 

[RUM4MO]

What was your original "aternator's failed" symptoms? Have you heard about the possability of the excitation wire being broken or breaking? There is not much that you can do to check an alternator resistance wise on its own as you will end up either looking back into the voltage regulator or if further in, the three phase rectifier - and that will not make much sense unless you separate the diode stack from the windings. Was the replacement alternator new or re-conditioned?

 

[DEAN0]

Right well im a bit nackerd with the alternator lark and have swapped to a new alternator. Can anyone tell me how test the alternator at the alternator using a multimeter. I need to identify if its a cable or if its the new alternator. The new alternator if anything is worse, so Im thinking either another duff alternator or a loose intermitent wire.

Any input much appreciated. Doubt its much good checking the battery at the battery side.

The easiest way to check altenator output IS at the battery.

Use a volt meter on the terminals and see if it's charging.

And +1 on the altenator load (excitation) wire being broken

 

[Guinness]

would just appear that the 70 amp alternator charges the car when the 120A doesnt, ruling the wire fault out. As if the wire was damaged then no charging would occur at all.

 

[richybigman]

When the car's running put a volt tester to the battery and it should read around 14.4v when being charged.

 

[Guinness]

which it doesnt do with the new one but does with the old one only about 3k revs

 

[richybigman]

You must have a bad connetion somewhere or a broken cable perhaps.

 

[Guinness]

yer but if it was a bad connection it wouldnt charge fine high up in the revs would it? nor would it have a problem charging with a damaged connection.

If the increased output allows the wire to carry the charge, then the new alternator should be able to do the same.