BmwolfJR 0 Report post Posted April 11, 2011 i need some help with the m20b25 i need to now how the alternator works and how to test one in the car thanks Quote Share this post Link to post Share on other sites
cliffdunedin 8 Report post Posted April 12, 2011 You'd be best to take it into a garage mate! Quote Share this post Link to post Share on other sites
hotwire 352 Report post Posted April 12, 2011 i need some help with the m20b25 i need to now how the alternator works and how to test one in the car thanks In the car? Key on - ign light should come on & go off when running. check voltage at battery - should be around 14v engine running Alt has two wires - a main battery supply & the w/l wire above. If the ign light doesn't come on with key on, earth the blue wire at the alt - light on = faulty alt, light still not on = wiring/bulb - w/light circuit. Make sure the alt battery supply is infact alive. Quote Share this post Link to post Share on other sites
