fc3stech

when I am driving a nite time all power and lights are fine but as soon as I drop below 1000 rpm and hit the brake pedal all the lights get real dim and the stereo makes a static noise, My car started doing this yesterday, my optima battery is not even a year old alternator is good, I am making the right voltage, I am guessing this is a grounding issue somewhere else, I also have a ground kit.

Could someone tell me or show picture locations of all the vehicles major ground locations or gives more ideas why this is happening, I know FC's have poor grounding issues and I dont want this to effect my ignition, I did a search as well didnt come up with anything

Icemark

sounds like the alt is starting to fail.

what is the voltage when this is happening. It needs to be at least 13.5 volts and preferably 14.4 volts.

Anything under 12.6 volts and there is insufficent power from the alt to run the car, and it is using battery power to keep every thing working.

So what makes you say:
what is the voltage??? why do you think the alt is good... sure sounds like it is starting to fail.

KompressorLOgic

iTrader: (6)

is there posibly a short with one of the brake lights?? or somthing??

i had an old car before that has some kind of short or somthing and id get a big voltage dip when id hit brakes. it would dim my lights and my sterio would cut out, sometimes the car would try to die even.

arghx

iTrader: (3)

alternator. Autozone or some place like that can test it for you.

fc3stech

I replaced the alternator in 03 and have only driven a couple thousand miles since, I used my multimeter and my turbo timer read 14 volts while above 1,000rpm when it falls below 1,000rpm it goes to between 11.56-12.47 volts,When I push the brake at above 1k its fine but at or below or idle pushing the brakes really robs electrical power causing dimiing of all lights and engine,and if I pump the brakes really fast it almost dies out completly

Icemark

Bad alt... it should never drop under 13.5 volts with the engine running, and dropping under 12.6 volts is radically low (you are running on battery power when that happens).

Sounds like you got a bad alt, if it is somewhat new

YearsOfDecay

What is the voltage across your battery with the car OFF???????????

wHAT type of optima... yellow or red?????

If it's below about 11.8 or so.... you got a dead cell in the optima

Also... clean the contacts of the battery, if they are corroded or munged up, its likely that you're not making enough of a charge...

Do you have underdrive pulleys on the car????

Do you have an E-Fan??????????????????????????

The alternator may be bad as Icemark states... BUT... if its pushin 14+ volts when the brakes and other accessories are NOT on and the car is at idle... then you have a bad circuit somewhere and voltage is being grounded to the chasis..

fc3stech

OK this morning I rechecked everything with a quality meter, I put the multimeter on my winshield to watch the voltage, with the car off the battery which is perfectly clean (optima yellow top) alone read 13.08, with car on and all lights off read at least 1386-14.0 with all the lights on at idle it read 12.46-12.80, so I guess this alternator sucks too, I have pretty much all stock lights basic stereo and h4 headlamps, well I guess I fill take this altternator in to get checked, well another question I have a s4TII and have an S5TII alt laying around are they interchangable, If so i will have them both checked

YearsOfDecay

s4 and s5 alt are PHYSICALLY interchangeable... however, when putting an s5 or fd al into an S4 car.. you have to run the wiring a bit different. the ring terminal is the same, but plug has to be spliced and one wire goes to the stock dash gauge wire and one goes directly to the battery. there is a post on here of the wiring diagram....



So... if you are going to use that s5 alt..... the ring terminal is normal

the L terminal goes to the White(black stripe) wire on the s4 harness and the s terminal goes to the battery... the black(white stripe) wire on the s4 harnes just gets taped off

Icemark

Ahh... that is called arc welding.

Seroiusly... wires melt, fuses blow, smoke issues forth, genies escape if wires a shorted to ground.