I'm getting ready to install LS1 fans in my 99 Sierra. I've got a 145 amp alternator to replace the original 105 amp job. The regulator pigtail for the 145has 2 wires as opposed to the single wire on the 105. Should i just solder them together and join them up to the harness wire? Thanks.

 

I'm not sure, but you may not need the 2nd wire, I believe that it is for a PCM controlled duty cycle for newer year vehicles. I had to run a wire from the PCM to the alt when I swapped in an 02 PCM into my 99, so if you're only changing the alt (and not the PCM), you "should" be OK

 

Google Nations Alternator.
You can call or E-mail them.
They will have an adapter or tell you what you can do to make it work.

 

I dont believe you need to do anything. I had a local shop build me a 200amp alt out of a 145 housing and I just plugged it straight in with my existing plug from the old 105amp alt.