Druken

ISo I tested my charging system and its reading 12.8v on the alternator and 12.7v on the battery but it says there's no charging signal. This is my second battery so it reads 12v but the other one dropped to 11v. Is this due to a bad alternator, bad regulator, or is it due to how I wired it? I have the b post wired to the 100a underhood fuse box which also connects to the battery, one of the plug wire connects to the battery directly, and the starter is connected directly to the battery. Hopefully I can fix this soon so I don't run through a whole bunch of batteries and the car is starting to run bad.

Icemark

Has nothing to do with the battery, but rather how you have wired the alternator.

What did you do? Install an non stock alternator or???

Is this a S4? a S5?

Little background goes a long way in getting help.

Druken

The alternator and motor are both s5 na but I changed the alt with one at kragen since my old one read bad and the new one read good. But I read it takes a couple of them to find a working one but I don't want to say its just the alt when it reads okay

Icemark

If it is only putting out 12 and half volts it is far from okay. Take it back and get another.

You do have the 2 pin plug on the back, plugged in... right?

HAILERS

And pull the small plug off on the back of the alternator and see if there's battery voltage on the wire on the left (looking into the back of the plug where the wires enter the plug, the wire on the left).

White with a Blue stripe on it according to the online FSM wiring.

Icemark

Then you have a bad alternator.

Did you get a rebuilt one or a remanufactured one? Rebuilt ones are just cleaned and the bad parts replaced, while remanufactured alts have everything that is not in perfect factory shape or could be worn in anyway replaced.

Druken

Yeah I think they only sell remanufactured alts. Its weird that thw alt reads good on their machine. What should the voltage reading be with a good workin alt?

Mr.FC3s

if your alt is in good shape it should put you at 14v at the battery. My rx was reading 13.8 at the battery. 12v is just the bare min. to run a car. Remember 12 is the magic number.

HAILERS

Like someone said, check the small plug for voltage with the plug on the alt and the key to ON, engine OFF.

somebody5788

Hmmm he might be right that there is no bottom end. A rotary doesn't have a head so no normal block to refer to as a bottom end haha.

somebody5788

wtf i must of posted this in the wrong thread...