Cadillac Repair: Car Wont Start, negative battery cable, neutral safety switch

Question
I have a 1995 Cadillac Seville SLS.  It won't start.  Everything in the car works.  The lights, horns, radio, etc.  I replaced the starter first.  Before I replaced the starter it would make a clicking sound.  My mechanic replaced the starter and it still would not start.  The mechanic did something with the battery cables and it started.  He said it was not the starter it was not making contact.  I drove the car again and the same thing happened it would not start.  I bought a new battery because I thought I had a dead cell because I would get a jump and it would start right up.  It started for a few days with no problems.  I drove it one day to the store, came back and got in my car and it would not start.  My husband tried to give my a jump, thinking the battery was dead and it still would not start.  Everything in the car is still working, lights, horn, radio, etc.  My husband said it was turning over but not fast enough, and it would not start.  Therefore, I had my car towed to the shop and am waiting to hear from my mechanic.    What do you think the problem could be?  

Answer
Hi Sheryl, Replacing the battery especially if it was the original was a good first step. Now testing the alternator and if there are any draws/computors or lights etc. that don't turn off thus draining the battery down. There is a negative battery cable that attaches near the front of the LF cylinder head if you have a northstar engine that might be loose. Otherwise if you have the 4.9liter the neg battery cable near the starter gets corroded and you will have slower cranking speeds. I wouldn't rule out the replacement starter as being good until it is tested. Battery cable connections need to be checked for being clean and tight. Also trying to start the engine in neutral would condem a bad neutral safety switch or one that is out of adjustment. The ignition key might be at fault or the lock cylinder wires could have an intermittant open. As you can see there are alot of possabilities and getting the car tested by a qualifity Caddy knowledgble tech is important to getting it fixed. I would be interested in knowing the fix. Bill