I've had previous problems with this before.

I've replaced the old alternator, and the battery both are under a year old.
The car was running fine for about 8 months then about last week the car battery has died on me 5 times.

When the car runs it runs at 12.1-12.2V max w/ the headlights on
When i tap the brake the volt meter goes down wen i press HARD on the brake it goes down to bout 9-10V.

It all happened after me and my friend were installing my new system into my car, however we did not hook up anything to anything ie. power to battery, or w/e.

The only thing tat was hooked up were the rcas from amp to deck, the front speakers were replaced and the wires are left exposed temporily, the remote wire is hooked up to deck, but not amp.

Otherwise I am stumped, I THINK its the deck... but i'm not sure...

Thank you for any advice in advance.

 

12.1-12.2v means the alternator isn't working, period. Throw a voltmeter on the battery terminals to make sure, but I'm betting the alternator is completely offline. Don't you get all the warning lights lit up?

-=Russ=-

 

Make sure your alt cable is secure at the big terminal up top...

Make sure the other end of that big cable is solidly spliced into the pos batt cable in the harness (might have to unwrap some tape for this)

Make sure your battery terminals are clean & tight...

Make sure the back small plug is secure on the alt...

Make sure your alt has a good ground (mounting hardware provides this- make sure it's all clean, metal-to-metal contact)

If, with car running, the above items are met, putting a meter on your battery terminals should net about 14.5 volts DC. If not, you have a bad alt...

 

When I gas, the volts go up slightly does that mean anything ?

 

Rev the engine to 3,000RPM to 4,000RPM - what are the voltage numbers now?


-Ted

 

W/o reving the engine its like 12-12.1 when i rev it , probably goes as high as 12.3-12.4 but once I hit the brakes it goes back down to 12 in no time.

 

That's not good, man...No wonder you're going through batteries...

Have all the conditions been satisfied from my first post?

Are you getting the alt warning at all while running? Warning panel lights, strange clicking sounds from near your left knee, that kind of thing?

 

u should be readin 13-14 volts easy when u give it gas

 

ok well when i give it gas it goes to 13V

I dont have a voltmeter so i cant check it at the terminals, im only determining the voltage from the volt meter in the dash, however the car seems to be running fine now.

The terminals are on tightly and nothing seems to be out of place so I think everything is ok for now.

 

Btw wayne there is no alternator light that comes on.

 

You have an S4? The voltmeter needle should be at or above the tick mark between the 12 and 16v marks, if everything (including the meter) is working correctly...

 

Well i did everything you listed,

i dont understand how my alternator could be dead

Could blown fuses be the cause of this too ?

 

Wait -- there is a cable from the alternator-> battery? Obviously this makes sense but my RX7 dosen't have this cable. It has 2 cables from the positive. 1 leading from the battery to the main fuse box in the engine compartment, and 1 directly to the starter. Where does the alternator -> battery cable run through to charge the battery? It should go through the main fuse box, no?

 

The only fuses that have anything to do with the alt's output is the 15A "eng" fuse- and if it was popped your main relay wouldn't be energizing, which means your car wouldn't be starting...And the 7.5A "meter" fuse. Are your meters, back-up lights, and warning lights working?

 

Henry, how are you charging the alt, then???

You're "charging cable" should run from the top stud of the alt to the harnesses you were refering to, spliced in to either the main batt pos cable, or the fuse box main, it wouldn't matter...Or, you could just install a new run from the alt directly to the batt positive terminal. In the OEM setup, according to the schematics (S4), it actually runs through the headlight fuse before charging the batt. Weird...

 

Yep - I find that odd. It was actually never brought to my attention up until this post. Then I remembered that I actually have no cable from the alternator -> battery. Odd.

I think I'll run an 8-gauge stereo cable from the alternator -> battery now. Thanks for bringing it to my attention.

While we're on the same note, maybe you can help me out with another problem: Everytime I roll down/up my windows and when I put the car in reverse, there is a strange beeping sound coming from underneath my dashboard near my left foot. What and why is this occuring? I figured it had something to do with a low-voltage situation...

Thanks