[cdalton08]

Hey everyone, I'm not sure if this is the right place for this type of question so sorry in advance!

2005 Mustang GT, 100% stock

Okay so last weekend my engine light came on and as I was driving to Pepboys by engine died. They said it was the alternator and that the battery was fine and just needed to be charged while I was driving. So Basically all they did was replace the alternator. About 8 hours later as I am heading out the battery light turns on and in the LED display it says "Check charging system". The battery meter looks about right (About 60% full like usual). My drive is about 30 minutes, and within that 30 minutes the battery light and LED warning turn on and off every 5 minutes. So I take it to Pepboys they test the battery and said it's fine and that I just need to drive it to charge the battery. For the next few days I drive it about 200 miles over a 4-5 hour span. The Battery light and "Check Charging System" warning now turns on about 1 minute after I turn on the car and stays on until I turn it off. The battery meter looks fine as well. I also read somewhere that it could be the wrong alternator that was put in and the on-board computer isn't recognizing it, could that be the problem? Like I said I went to Pepboys and I would assume a big company like that knows what they are doing. The car runs perfectly fine except for those warnings but I am afraid it will die on me again. Any reason why this is happening?

Thanks in advance guys!

[Mr.Stang08]

Hi Cdalton I'm just running thru the same exact problem. These stangs tend to have this problem with the alternator. Ford installed a weak one on these. I ordered my alternator thru www.paperformance.com. They have a higher performance alternator that is better than the stock one and more economical with lifetime warranty. I am actualy waiting on a 4 gage wire to install everything from american muscle. Good luck with you situation. I'll let you know how mine goes. I'm installing mine on Dec 1st. I will provbably need to get a new battery as well to keep everything fresh and with a good start. Will keep you posted. Oh, and welcome to the forum!!! and yes you posted on the wrong section even thou it's general tech. You should go to the 05 section.

[mxnate116]

sounds like a loose connection check all the wiring on the alt

[1rnkpny]

Normally it is the regulator that controls the operation of the Battery light. Do you have any corrosion/rust around the battery terminals or the battery ground on the body?

[mustangmallory]

I know this is probably off in left field, but I've been dealing with similiar issues here with other Mustang owners. Fortunately I saved a lot of money as other people dealt with it before I had to. If you have an aftermarket radio in the car, but not amps or anything else there is a wiring issue. The factory amp uses a 5volt trigger to turn on. A lot of people in this situation notice the annoying amp pop when you first start the car. The problem is that most harness adapters wire the amps to be on all the time, which leads to dead batteries and what a lot of people would think were bad alternators. I only saw in two cases that the car actually picked up an error could related to this problem. It's really a simple fix of rewiring the ground and power lines of the amps, while adding in a very cheap resistor inline with the power wire. Eliminates the charging issue and amp pop problem. Like I said, I'm probably off target here, but something to consider or might help someone else.

[1rnkpny]

Originally Posted by mustangmallory The problem is that most harness adapters wire the amps to be on all the time, which leads to dead batteries and what a lot of people would think were bad alternators.

An alternator wouldn't test bad because an amp is turned on. I have seen an alternator test low beacause of a bad battery. Modern AVR testers use the high beams and heater fans as loads to check the alternators capabilities. If people replace alternators because they THINK they're bad, then I guess their perogative. But hey, stranger things have happened with electrical issues.