2001 ford taurus ses battery/starter issue???

I could use some help figuring out what might sound like a dumb question. I have some limited mechanical apptitude, I used to do all my own work on my vehicles up until I bought my 87 Ford Escort. From that car on I just have problems with the new (improved?) computer complicated engines and their components in the newer cars. That being said... My Taurus was not exactly clicking when I turn the key, it's more like a grinding click, I thougt about the starter first thing but like I said it really doesn't sound like a typical "starter clicking" sound. I'd hold the key until it finally started, well now when I go out to my car first thing in the morning it won't start, so first I cleaned both terminal, and it started fine. but after not running it for about 8 hours it went back to not starting at all. So, then i noticed some corrosion on the 'thinner red' wire connected to the "positive" terminal so I cleaned it and the car started! I thought I found my issue... but again after sitting all day at work it wouldn't start again, i can start the car immediately after driving it every 3 or so hours but let it sit for 6 or more and all I get is the grinding click. ***to start my car I need to loosen and re-tighten the skinny red wire and behold! the car starts like new*** what is that skinny red wire? where does it go? why does the car start simply from loosening it and tightening it back up???
can anyone shed some light on this??? sorry for the long explanantion but I don't want to miss any of the small details that can be useful.
thanks in advance to anyone that can help me.

Welcome to the forum!

How is this skinny red wire attached to the battery terminal? If it's on a ring terminal and held on by the battery terminal bolt, that is aftermarket and not something anyone here is going to be able to definitively tell you where it goes, unless you're driving their former car.

Currently, when the car won't start, are you getting any sound from the starter motor?

It sounds to me like someone may added an aftermarket alarm system or remote starter system on your car and ran a separate wire to the battery for the starter disable relay. If the skinny red wire is not getting a clean connection to the battery, the starter disable relay may be remaining open, preventing the starter from trying to engage.

Assuming this is an aftermarket wire and connector, there's a good chance the ring terminal is just crimped on to the copper wire and is therefore quite corroded by now, contributing to the problem with only making intermittent connection.

-Rod

thank you for your response, actually, the skinny red wire is nothing "after market" it powers up my clock and stereo programing. It runs into the fuse box via a harness it is wired into. why it had anything to do with making the car start i seriously do not know, i didn't troubleshoot which fuse it actually goes to and in turn what all that particular fuse powers up. what i did was check my battery, i really didn't think this was the problem but a good troubleshooting begins at the... well, beginning... so i checked the battery and it was putting out only 9 volts! i put in a new battery and viola! problem solved ever since.

Double check your alternator output.

done and done... the car is running just fine now.

thanks.