Electrical problems

I have a '99 gt convertible, and about 11 months ago the mach 460 system started having problems. Occasionally when listening to the radio, it would switch over to CD for a half a second, then back to radio (with or without a cd inside.). This problem became more and more frequent until the radio was unlistenable.

I figured the problem laid between the cassette/radio Head Unit, and the CD Player HU (both stock). So I bought an Insignia HU (which I love), and it worked great.

Everything was working perfectly for months. I then left the country for 3 months and unfortunately for me, my family didn't think of turning over the engine of my car every so often until it was too late. I came back in January, and naturally the car battery was dead. We tried to jump it but no success. We ended up buying a new battery.

A week later the weather turned bad so it was raining alot and the convertible tends to leak in a little water so I prefer to drive another car during that time. about 9 days later, the new battery is dead. I had AAA jump the car. The tow truck guy told me that the altenator was fine (I dunno much about that. I'm a computer guy. I don't know what or how he checked so maybe he's wrong).

A while after that the car battery goes dead again even though I had driven it the day before. Jumped it, worked for a while, rained, didn't use for 5 days, now it's dead again. Last time I tried to start it though my speakers were making a loud humming sound with the little juice left in the battery. Unplugged the head unit and of course the sound went away.

I would suspect the altenator however with past issues with the previous head unit, and the new Humm from the speakers I am not so sure anymore. I think maybe there might be a short with a wire somewhere, but then again, i'm new to car troubleshooting, I just know how to drive them.

If it is wire issues, how much should I be expecting to save up to run new wires through? any ball park figures? Any other issues it could be? I checked the fuses all the small ones checked out fine (I didn't have anything to grab onto the larger fuses to check those out at the time, however I do believe the stereo fuses are the smaller ones.)

P.S. my GT is stock with the exception of upgraded gear ratios and rims.

Sorry, one quick thing I forgot to mention. Everytime I jump the car, the car alarm goes off. I assumed that was natural, but is it?

Sorry for the long post, I just wanted to make sure all the important info was there, seeing as how I don't think I am qualified to judge whats important and not.

I currently disconnected the head unit. Tomorrow I'll try jumping the car and we'll see what happens from there. I am waiting on a commission check to come in before I take it to a shop.

As for disconnecting the car alarm, I'm no thief, I dunno how to go about that. Any links or advice? I assume it's a stock alarm, the previous owner made no mention of any upgrade to the alarm.

About what you said about the cd player kicking out. If it was a sign of the alternator, wouldn't my replacement unit be doing the same thing?

As soon as some money comes in, I'll get the car into a shop. I'm just hoping there is something I can do in the mean-time.

Ok so here's the update for my situation.

I pulled out the alternator only to find out that both kragen, autozone, and the local ford dealer do not have the connecters to test a '99 mustang gt's alternator. Both the Ford Dealer and Autozone said they could test the altenator inside the car.

So I decided to hook the altnerator back up, jump the car, and go get it checked. As I went driving down the hill I live on it started raining and hailing like hell, so I had the windshield wipers on.

When I got to the base of my hill (of course the base) the power went out. So I had to get it jumped again, it was almost 6 pm, figured the place would be closed by the time I got there, so I am gonna try to get the car tested tomorrow.

With the power going out like that while driving. I am now believing that it's probably the alternator. My stereo was completely disconnected while I was driving. only things I had turned on was the wipers and the dash lights.

Today there was no electricity in my car at all, not even the chime when you open the door or faint lights in the dash. not a single volt of juice. Despite having the vehicle running yesterday.

I called my local ford dealer and yesterday the man I talked with ( I wish I got his name) told me he would test the alternator for free. Today they wanted to charge me $160 diagnostics, plus installation labor and of course cost for the part.

Autozone said they'd test it for free. I asked them how long it would take and they said less then 5 minutes. So now i'm worried that autozone will just run the same test as the AAA guy did.

For $160 diagnotics, I might as well say screw the diagnostics, and just buy a new alternator. Is there anything else I can do? I don't want to end up buying a new alternator if the old one is good and there is a different problem.

I've also read about people buying faulty alternators new. If nobody can bench test the alternator outside of the car, then they won't be able to bench test the new one either.

Ok, I decided screw it and was gonna go out and buy a new alternator. I was looking online and everyone wants to charge this "Core" price.

Is the core a component of the alternator? I don't really know what it is, but supposedly i can return it. Is it something I need? I'm tight for cash right now so I'll have to hold off If I do require the core, but if not I should be able to get by.

I also see a few different alternators, anything I should be looking for when purchasing one? I see some are 110 amps, others are 130. I know with electricity, more doesn't always mean better. I am using Kragen and autozones site so supposedly I am looking at the right ones for my car, but I don't know if the site is accurate. What should I be looking for?