I,ve got 3 third gens had 4.one died.an 89 iroc 5.7 stock an 90 rs that was 5.0tbi and a 86 bird with 2.8maf system but a 3.1 sepentine beltsystem on it.heres my trouble,the 86 was a basket case.I got it running with stock ecm engine harness and such.there were only 3wires on the old altnator.1red(big) one red small and one brown.the newer alt conector is the same.now the large wire gose to a juction buy the radiator.the other two go down to the starter,the iroc dosnt have 4 wires either and the wire coming off the alt gose to the battery not a junction near the rad,the 90 tbi and the old dead bird both 90 modles went to a juction like the 86.Why dosnt the 89 iroc go to the same kind of junction?has sombody changed this area?the book gives the 86 and 89 as same charging systems and the 2 90 modles should have been different.will my 86 charge ok without the 4th wire?my dumby light dosnt come on when the key is turned on.right now I got an old none working alt in the car as I test the rest of the stuff out.But almost done with the other stuff and ready to buy one.