My 2004 F-150 V8 4.6 has been barely starting all winter. I finally went and got a new battery and installed it the other night. While doing this in the dark in the wal-mart parking lot ... I didn't attach a wire that connects to the positive terminal. I realized this when the truck lights were going dim the next day. I got home and reattached the wire -which goes to the alternator. Thought my problem was solved but my truck wouldn't start this morning. I jumped it off and then it died on the way to work. Battery light came on which means the battery isn't charging properly. Did I mess up something? Is the alternator bad or did I just blow a fuse or something? Thanks for all the help!

I found this article if I need to replace the alternator ...

How to replace the alternator on your 2004-2009 Ford F-150. 4.6/5.4 engine size

Things You'll Need:
Socket set
Small pliers

Step 1. Always disconnect the negative terminal of the battery ...ALWAYS!!!!
Step 2. Remove the alternator drive belt. To do this, you need to locate the tension pulley. It has a spot where it allows you to use just the drive part of your ratchet. Insert and push to release tension and remove the belt.
Step 3. Next, remove the alternator harness clip. You will need to pry this off.
Step 4. Now remove the (4) support bracket bolts and remove the bracket.
Step 5. It's time to remove the alternator B+ terminal nut and disconnect the battery cable from the B+ terminal. Then disconnect the electrical connector from the alternator.
Step 6. Remove the (2) lower alternator mounting bolts and now remove the alternator.
Step 7. Installation is the reverse of these steps. Good luck and refer to a manual when needed.

 

Might want to have the new battery tested 1st, could be you ran it completely dead.
I would not think this to be the alternator, as it is PCM controlled. Not sure which wire you are talking about leaving off.

Is this a 2004 New Body style or a 2004 Heritage / lightning model ?

 

New body style. I connected the main pos/neg connectors with the new battery. There are also two extra wires that connect to the positive connector on the battery. I connected one of them, but left one off when I hooked up the new battery. Thanks for the help!!

 

Here is a pic that I found. Under the red connector ... several wires come out.

After I noticed my lights last night, I got home and found the loose wire and reconnected it. It started right up after that, but this morning it would't crank at all. I jumped it off and charged it for a few minutes ... then left for work. It died 3 times on the way and I had to get my wife to come jump/charge me up. The battery light kept coming on which means (not charged properly) and then service engine soon light came on.

 

the 3 wires should be

1. CJB ( aka Central Junction Box / cab fuse panel )
2. Starter motor
3. to Fusible links A & B

The cable you left off is the Black w/ orange stripe wire, that has a splice ( S119 ) , to the 2 fusible links, to another splice ( S120 ).
Splice S120 is 4 wire ( 2 to the fusible links above ) and 1 to another fusible link, then to the alternator, the other is direct to the alternator.

I am going to take a SWAG and say the new battery ( which never got fully charged ) was drained too low. Might come back with a trickle charger over night, but considering it is brand new, take it back and have it tested.

The battery light could mean a few things, like the battery not taking a charge ( from being killed dead powering the truck ).

Prior to digging into too much, start with having the battery load tested.

The CEL could be any number of things, without the DTC #, no sense guessing. Also could be due to the battery condition ( battery trashed from running too low, and requiring too much from the truck to charge it again / outside normal charge parameters ).

 

Here is a pic I just took. I went and jumped the truck off and made it to my local service shop. My battery light and service engine soon light were still on. The only wire I left off was the top wire that runs down with the orange stripe. I can't believe I left that wire off when I added the new battery, hope I didn't screw up and cause this problem. I will let you know what the shop says ...

 

The shop replaced my alternator and everything seems fine. Except the $388 bill.