So i bought a 2008 bullitt about 2 months ago. it has 93k miles on the dash. Since ive bought it ive had to do some work on it. My issue is ive had to replace the battery and alternator 3 times now, and im about to take it to the shop tomorrow for an AC compressor only to find out when i go to start it today. I have a no crank. The charging system did say to check it yesterday but it disappeared and voltage stayed high when driving so i thought it was fine. i had this same issue on my previous 2002 V6 SN95. I got curious and started to check voltage and see maybe if there's some resistance. My battery cables and connectors are corroded a bit which i wanted to get done. the last time i got the parts changed was about 2-3 weeks ago. the first time i changed it i did it my self only for it to die in 2 weeks, then i took it to a electrical shop. they did the battery and alternator. it blew again 2 days later, they then replaced it again for free (warranty) only now it blew again. Im taking it to the shop to do the compressor but now i need to get the alternator and battery done because theres 1.4Vs and apparently 9.9 M ohms. idk how there's 9.9 million ohms through my battery. i tested that from post to post, cable to cable. battery to alternator and battery to block as the block is also a ground for the alternator and still got 1.4V and 9.9 M ohms. This is my only car and i want to fix it before saying the hell with it and sell it, i really love this car. and ive put about 5 grand from a rear end replacement and 3 alternator and battery changes which are about $500-$600 a trip. Could nayone tell me whats going on with it. Cause im confused even my friends are confused and they both have mustangs. 1 of my buddies works at a dealership as a tech and has never seen something like this before. again this happened to my old SN95 as well, in total ive probbaly had 6 alternators and 7 batteries put through both my SN95 and my SN197 bullitt in the last 2 years. Im getting very annoyed and dont wanna just get rid of this car.

 

Just to add, i paid about 18k for this car tag and plate included plus dealer fee. I know i probably scammed myself but it was something i really really wanted mainly because of my grandfather and his love for cars that pay homage to classics. It may not be worth 18k to others but she is to me because its something i love. Now i sold my old mustang because of insurance because at the time i had 2 cars but i sold that other car too leaving me with nothing but then i bought this. Im in the works of buying a truck and eventually taking this to be a project of swapping it to a 5.0 again i dont want to get rid of it and i want it to last a little bit longer before she can rest for a bit when i get my truck but if i cant get on top of this issue now. Shell probbaly go to an auction or even worse a scrap yard and thatll hurt seeing a rare piece like this get tossed. I would really love to fix this issue before it comes back again, when shes running she has 0 issue getting up to speed like shes supposed to. no wierd noises other than the usual mustang vibrations and squeaky suspension parts that need tuning. but other than that shes an A1 beast. Its just this electrical issue thats killing her. I read some where it could be as simple as a fuse or as pricy as the ECU. Im willing to repair anything i need to, to keep it running. i just need it done asap before it becomes a permeant issue.

 

Also, I know theres a possibility of it being a dead cell. But after 3 changes youd think that issue would be ironed out. Im just having trouble figuring it out on my own and the shops arent helping by just replacing the same part over and over again with no explanation.

 

Where are you getting your alternators from? Most rebuilt are garbage because they don't replace stuff that still "works" meaning the rectifier assembly.
Also, have you checked for phantom voltage drains or bad grounds?

 

I’ve got the first one from Auto zone, the next 2 we’re from an electrical shop I live by because I was leaving town and didn’t wanna return to a dead car. According to the shop it’s at now for the 4th alt, the battery is fine but the pulley on the alt was shot and the belt too. I’m not sure if the belt was shot before hand from the previous 3 alts. But I’m hoping this fixes it now. I had this issue in my sn95 which I ended up getting rid of cause it was too expensive to keep repairing battery and alternator issues

 

i just got the car back from shop, they said my belt was bad and caused the alternator shaft to crack in half which caused my A/C to go out as well cause it wasn’t really turning right. When they put a new alt and belt on the A/C kicked on perfectly like it should have which it had not been doing since I bought the car. So we are all in agreement that the belt was causing failures to the charging system and causing the A/C to fail because it wasn’t spinning the pulleys correctly on either. What do you think?

 

An auto electric shop usually knows what they’re doing on electrical vs a regular shop. These cars do have a clutched pulley so if it froze or something else was having issues it can cause failures.

Is their explanation plausible? Yes, but not highly likely. If everything is working though, then there ya go.

 

hey so I know this is a month later, the car ate another one. I bought a pa performance alternator with a max rpm limit of 16000, wel I found out my cars issue is 6.5” crank pulley, with a 2.36” alt pulley mixed with a 6500 red line, well. That’s around 17800 RPMs which is why the dues last ones kept going bad from the shops. Well, I bought a bigger pulley for the alternator, a 2.9” which lowers my ratio and drops my alternator RPMs to 14600 ish out of the max 16000. So I think I should be ok, what’s your thoughts?

 

Underdrive pulleys are usually a waste and cause more problems than what they're worth....Put your pulley's back to stock and start clean to see if that gets rid of your battery/alt issues. If it does, you found your problem.

You said you had the same Alt/battery issues with your SN95? What mods did it have?

One car with the batt/alt issues ok, but two. If they both had the same mods.....

 

so the sn95 was a v6 but had 187k miles on it. The alternators weren’t blowing the same way a they are on this one, the sn95 just kept dying on me and the batteries would kill the alternator and the alternator would then kill the battery. I gave up on that car and sold it to my buddy and according to him, it’s running on 2 cylinder, cracked trans and a cracked block. But he’s swapping the motor anyways. The problem I have now was I didn’t get under drive pulleys I just bought a bigger alternator pulley as it was a fix for many other people. The problem is ford gave this car a redline of 6500 rpms, alternator pulley size of 2.36” and a crank pulley of 6.5”. Doing the math my car is spinning alternators at around 17800 rpm which is way higher than most alternators can handle. So buying the bigger pulley to go on would spin the alternator slower while maintaining the charging. I bought a PA performance alternator installed a 2.9 inch pulley onto it and through it on. Well today after I did all that, the nut that holds the pulley on it. Dug into the pulley shredding it and spreading parts of the rear of the pulley as well. The belt then slipped off cause the pulley came really loose and my car over heated and shot coolant from god knows where. I checked my oil and haven’t seen any coolant contamination which is a good sign but I’m still worried. I had to towed back home and I noticed the pulley I put on the backside does not match up to what the stock pulley looked like. So I’m trying to find a pulley that has the same backend to it to sit on the alternator but I still need the 2.9”-3” size pulley to prevent my car from over spinning the alternator. It hasn’t been tuned so no limiter has been changed. From the looks of it the alternator seems to be ok and the pulley took all the damage but I’m gonna be pulling the alternator later and seeing for sure. I tried to spin it by hand and it spun both ways but also stopped both ways after half a spin. So I’m not sure and again, I’m worried.