dimming Lights

[Dave0803]

I have an 03 GT and my voltage seems to fluctuate a lot. sometimes I have even seen it drop to almost 12 Volts when a lot of power is drawn (when A/C compressor kicks in, both windows going up or down, etc.). What I wondered about the most though is when I press the brakes I can see my lights dimm and a drop in voltage. Is this normal for these cars? I have had the alt. replaced and everything checked.

 

[exindust]

Battery?

 

[fluffyrunnells]

yellow top..ftw

 

[4.6_02_Black_GT]

You mentioned your voltage is at 12 volts, is this at idle or 1000+ rpms?? If you r engine speed is anything north of 1000 rpms the alternator should be able to deliver a constant 13.5-14 volts back to the battery. If the alternator is new and you know its good, I would possibly check your ground wires. Once your stang is moving even if your battery is shot the altenator should still deliver 14 volts to the electrical system...of course if you stop a light and your battery is gone..the stang will die.

..recommendation wouldnt hurt to swap batteries..but your problem could be ground related.

 

[Dave0803]

it does deliver 13.5-14 volts. It just seems to drop/fluctuate a lot whenever any power accessory is used like the a/c, power windows and when I use the barkes the lights all fliker. I also noticed that when the a/c comes on, the idles drops to about 500 rpm for a second. I don't know if all these car do it, but most cars the idle will be raised a little when the a/c comes on. My girlfriends 4 banger doesn't even drop idle rpm when the a/c comes on.