Joined: 19 Aug 2007
User's Age: (56)
|Posted: Mon, Jul 28 2014, 9:03 am Post subject: voltage drop testing. something simple to find gremlins.
|i run into a LOT of electrical issues on cars and trucks.. repeated alternator failures. surging lights or dim lights... multiple computer codes..
you may want to save this image to your computer or print some copies..
want to have some fun.. walk out to your daily drivers and run this test.. if the alternator is Hard to get at.. skip test 6.. but i have found 3 volts on test six on a LOT of cars and trucks.. that requires cleaning of the improperly tightened output stud fastener and ring terminal.. replacing the end of the output wire near the battery or the under hood fuse block..
there was a 2005/06 caravan that had surging/flashing lights after a motorized door was used.. many owners had spent thousands of dollars in repairs. including new underhood relay boxes, replacement PCMs. replacement alternators, replacement batteries, new wiring harnesses.. when the issue was actually skipped over by the techs.. where the 3 battery cables come off the positive battery terminal and are crimped together in a ring terminal.. the crimp is loose. one wire to the starter. one to the underhood relay box.. one to the alternator. when the system had a heavy load. the voltage thru the loose crimp dropped. this caused the computer that is powered thru the underhood relay box to request more alternator output.. this created a see saw effect and surging/flashing lights happened..