Hate to ask but, I just purchased a 1986 Pontiac TransAm, 305 v8, previous owner put a 1992 305 engine in. He cut the original alternator wires. What is left is 3 original wires, a thick red wire which I know goes to the lug on the back of the alt, but there are 2 more wires, one red, one black or brown, cant tell for sure. the new alternator has a 4 prong plug, with one plug larger then the other 3.

markings on the plug are PL FS

does anyone know which wire would go on the bigger prong, ( im assuming the red )
and where does the other wire go ( f ) ?? or " L" ??

thanks for any info...................

Rich

 

In 1986 the Camaros came with a 12SI style alternator. It has 2 wires going to a plug that plugs into the internal regulator, and there is a large wire that goes from the battery to the back of the alternator.

Later on, GM switched to a different style alternator, the CS series, which has the weird shaped plug, like a small "L". Depending on the year, engine, etc different wires were actually used inside the plug.

(You didnt mention if you are using the stock 86 harness or the 92 engine harness, so I am going to assume that you are using the 86 setup.)

You can either make an adapter to convert from SI to CS style or buy one. You just need to know if your car has the "no charge" light or not. If it doesnt', you need a resister on one of the wires. IIRC, its the L terminal. I believe that the other wire that is used is the S terminal.

If it were my car, I would buy a stock SI plug, figure out the stock wires and install a new SI plug on the car and buy the adapter from Napa part# EC82 (with resistor). Clean install.

You can probably find out which wire goes where, just do a search for SI to CS conversion. You can also look up vehicle wiring diagrams at autozone.com, you sign up for a free profile and go through vehicle repair.

Tons of info in this thread:
https://www.thirdgen.org/forums/elec...ed-up-alt.html

 

thanks for all your time and help........ !