I have a 1994 nissan altima that won't start. When I turn the key on it will act as if it wants to start but will not turn completely over. I recently had a friend replace the headlight connectors on it and after that is when it wouldn't start. One of the connectors went bad so we replaced it with a connector that was taken from a different nissan and "spliced" to the existing connector. could this have something to do with it not starting? HELP!

Well do your light work? How about your fuel pump fuse?

I've been told that it's the power transistor for the ignition system....does that make sense?

True, but I would go with the easy stuff first. check if your battery is good, get it tested under load, also make sure your battery connectins are good. Fuel pump fuse, starter relay, ignition mod. fuse (if applicable.)

First see if your getting fuel and spark.2nd if not check all the relays and stuff.Check the batt next hell might even want to try to jump it lol if it works jumping it you have a going bye bye battery.Remember KISS