I have an 87 GT. Before winter, I replaced the battery, Alt. I started the car up a month ago and it ran STRONG with no problems. Today I went to start it up and it started no problem. I noticed the battery gauge in the dash was a little low but though nothing of it. I drive to car up the driveway and let it sit/run for like 15-30mins. I looked at the gauge and it was alot more lower. I shut the car off and then it won't start up (Clicking). Went out to buy another Alt (Wrong fit) but it starting up. Runs a littile ruff. Its like the alternator isn't charging the system. The car has sat so I m guessing I might have some corrosion on a wire.I m not dump, but when it comes to electrical stuff I m an idiot.I m going to get a new alt. but I have a feeling it might be a conections. Where do these wires run (Location).Any help !!!

 

With the key on engine off, the gauge will give you the battery voltage. With the engine running the gauge will give you the alternator output.

Should it turn outnot be the alternator...

With the car sitting so long the battery may have simply lost its charge if it got too cold. If your battery has caps pry them off and look inside each hole. If the levels low it wont hold a charge for long.Use distilled water. If there arent any caps look for a little clear dot. Green is good, red is bad. Youll need a new battery if its red.

Check the alt connectionsto make sure everythings tight and clean. Same for the battery. Check the belts to make they arent too tightor too loose. You can use a mix of baking soda and water with an old toothbrush to clean the terminals if you dont have a wire brush. It works.

Check everything under the coil cover if you still have it. The black cable from the battery goes to the starter. Id check that to just because.