new alt, new battery same problem???
 

ok so the problem is i turn on my car my voltage then stays at 12v and slowly drops as i leave the car running so the battery is not charging.

Every thing is clipped in i have conitinuity (i am sorry for my spelling i would normally look up words but im tired) from the out side of the ALT to ground and i have continuity from the power post on the ALT to the battery

Now the clip in the back of the ALT has 12volts on the top tang when in ACC and when car is running

The bottom tang has ~7volts when car is in ACC and when running

With the key in the off position the top tang continuities to ground and the bottom tang does not

I assume the top tang should not be going to groung when key is in the off position

any help would be great ill check the post every 5 minutes or so while im trying to figure out wiring diagrams and eat dinner

i read the faq and searched but only came up with bad altenator responces O and the altenator i bought is new not rebuilt

thankyou again for any help/suggestions

With the car running you should have 14.4 volts on the alternators main terminal.

Not 12 volts.

Anytime there is less than 12.6 volts, the car is running on the battery.

Your alternator is not working. You have either installed it wrong or it is bad.

And your bump has been deleted, bumps are forbidden here in the 2nd gen RX-7 technical section

ok so i went and grabbed my buddies altenator off his car which worked 5 minutes before i pulled it off. I hooked his altenator up to mine and for the hell of it i put mine on his and started his car. My altenator worked on his car 14.4volts but his altenator did nothing to my car its still running off the battery and the altenator is not functioning on mine any ideas??? it is all hooked up correctly

-thankyou

series car and series alternator???

what modifcations or changes have been made??? sounds like the two pin plug is not pluggd in or wired wrong

Put da small plug back ON the alt. Turn the key to ON, ONLY ON. Backprobe the bottom wire on the alt plug (should be White/Black). It should read approx 3vdc.

Measure the top wire by backprobing it (Black/White wire. It should read 12vdc. It should also read 12vdc with the plug off the alt when the key is to ON.

With the key to ON, the Warning LIghts should be all lit up.

It's normal for the spade on the back of the alt where the white/black wire goes, to put out a GROUND. It puts this gnd on the alt relay in the CPU on a S4 which in turn makes the Warning Lights come ON. It does this anytime the alt is not putting out.

This should get your post back to the top. I've no idea what's wrong with your car.

are you saying the warning lighs wont be on (with the key in on position) if the alt isnt working properly?

also are there any major problems (besides install) with an fd alt on an fc?

yeah it wires, completely different than a S4 FC alt

Is that the problem??? You have been trying to put in a FD alt and wasted all this time and space by not saying so???

my friend dantheman94080 said that he is using the same exact alt. a brand new s4 alt. oh and he sees warning lights when the keys are in the ON position.

I'm just saying that on a series four car and series four alternator with series four stock wiring, if the key is put just to ON, the Warning Lights light up because the alternator when not putting out, will put out a ground on the white/black wire which in turn pulls a relay in which in turn applies 12v to the Warning Lights and turns them all on.

Once the alternator puts out with the engine running, the ground above no longer exists and the relay in the CPU relaxes and takes the 12c away from the Warning Light circuit. A bum relay in the CPU could have done the same.

I was just curious if, when the engine was running, whether or not ALL the warning lights were on or not.

If this problem is not with a series four alternator in a series four car with stock series four wiring, then I've no clue what the problem is.

ON a few alternators that have no input to the two wires on the back of the alternator, if you rev the engine up to over three grand or so, they will put out. Some alternators will do that, and others won't . It's still a broken system even if it does.

its a stock s4 alt i have a sound system which i ofcoarse disconnected before trouble shooting anything in the car and the car is an s4
reving to 3 grand does nothing i will go pop a meter on the plug really quick be back in 5

So? When the engine is running do all the warning lights come on?

When running, and you put a meter on the large wire on the alt, what does that meter read? Maybe you have voltage there but the output wire from tha alt to the engine fuse box is kaput. As in the alt might be putting out but the large wire has an open?

ok yesterday when starting warning lights would come on today they didnt does this mean that the fuseable link is blown? or that the ecu is having issues

If the warning lights are not coming on, the 2 pin plug on the back of the alt is not plugged in or the alt is bad or your CPU is unplugged.

If the 2 pin plug is not plugged in the back of the alt, the alt would not charge either.

the 2 pin plug is plugged in i dont see how the cpu could get un plugged ill take the alt down to my dads shop tomorrow and bench test it after work

well on a S4 (you still have not said what you have) the CPU has a relay that triggers all the idiot lights.

But it has nothing to do with charging.

so if you are not charging, and the idiot lights are not on, then the two pin plug is not plugged in.

im sorry i have an 87 base

I am sorta having the same problem. I have a 87 t2 with a S5 alternator wired in. I have had this setup up for over a year. Just recently i have been having electrical issues. I have cleaned all the stock grounds, Replaced the battery terminals, and replaced the alternator. I start off charging at 14.5 (perfect in my opinion) and after about 10 minutes of running the charging system goes down to 13.6 (normal) but when i drive i see alot of 12.6 readings. I am about to try changing the postive and negitive wires and terminals out for brand new one (stock 19 year old ones still there) and change my battery( possible internally shot).

If I were you i would definately piggy tail back on your signal wires as they sound like they are not hooked up properly.
Thats were i would start. Also check and clean your terminals huge help when i first started having a low charge .