second gen battery dying
 

hi guys i'm pretty much new to rx7 so please help me out...thanks in advance....ok i just bought a second gen n/a and somehow the battery keep getting drain overnight if its fully charge....but if i jump start it it'll start and run fine and if the battery is dead and i jump start it and drive it until it reaches normal temperature then turn it off and check it with the volt meter you can see the voltage drop like .1 volt every 5 second....so i really not sure whats the problem.....i was thinking altenator? belt? again thanks for any help

Right after shutting the engine off, there will be a surface charge on the battery. It's normal for voltage to be slightly above normal for a short period, so you can watch it decrease slowly. But if it is draining down past ~12.5 vdc, there is a short somewhere in your wiring.

You can check the belt tension on the alternator pretty easily, and you can also put a multimeter on the B-post to see the output with the engine running. 14+ vdc is ideal, and if it's much lower than that, the battery isn't going to be charging properly.

so if its a short can you get me an idea on where to start and how do i check for shorts....sorry i'm not good with electrical stuff...and yes when i turn it off it drops below 12.5v and keeps going down....and does the alternator or belt play a role in the battery draining while the car's turn off? can you tell me where to find this b-post? thank you

There are different ways to go about this. You could have your voltmeter connected to the battery as in red meter terminal on the positive battery post and the black meter lead on the negative battery post with the meter set to voltage DC (vdc). Do this right after turning the car off and start pulling fuses one by one until the battery drain stops. The fuses you want to focus on are in the engine fuse box first and most notably the BTN fuse. See if you can narrow down your problem this way and get back to us with the results.

EDIT: Be careful not to yank out the "main fuse" because it is screwed into place.

thanks alot.....i'll give it a shot and post what i find.....

ok, so i try pulling off all the fuse one at a time after the engine was turn off and somehow it seems to make the voltage drop faster now....even after i put all the fuse back....and it is normal for that sqaure thing ( sorry don't know what that thing is called) that was bolted to the fender wall next to the ignition coil ( trailing side close to the driver) to make a clicking sound when you unplug one battery cable then put it back? oh and i check the battery voltage at idle again and it say 11.40 (900 rpm) and when rev it up to 2k rpm it says 12.64v.....so does that mean my alternator's not charging?

The "square thing" sounds like the main relay. If the battery is disconnected, there should be no way the relay can be activated.

It does sound like your alternator is not charging. You should be getting about 14 vdc output, so 11.4 to 12.6 vdc is not good. You can remove the alternator and take it to an auto parts store for confirmation.

ok so will the main relay make a clicking noise when you reconnect the positive or negative cable after you disconnect it ( like you disconnect one of the battery cable and then reconnect it) ......and i'll have the alternator check....but if the alternator is at fault, will it drain the battery when the engines off?......

With the key to off check to see if there is voltage present on the Black/Yellow wire at either coil,trailing or leading. If there is then the main relay is not operating properly. Also, if there is voltage present with the key to off on the Black/White wire at any of the emission solenoids that are part of the rats nest then again it indicates a main relay that is not operating properly.

by key to off, you mean lock position right? and the blk/yellow wire are the two prone wire correct? i check those right after the engine warm up and the voltage read .019 (by having the blk lead to the negative battery and red to the blk/yellow wire) on both the leading and trailling coil.....somehow during the precess i forgot to plug the leading coil wire back in and try to start the engine but it wont start, then i realize that i forgot that and after i plug it in and turn the engine off, i check the battery voltage and now it reads 12.49 and it seems to be constant no dropping.....so i'll check it again later to see if its draining or not.....oh yea and after that i try checking the main relay if its making that clicking sound when reconnecting the battery and it doen't do it anymore? does that mean anything? and i'll have the alternator check today......

The main relay allows voltage to be present on the B/Y wire when the key is to on. It's possible that the relay has been allowing voltage to be present on the B/Y wire when the key is to off and this could explain why the battery voltage weakens over time although the culprit for the voltage drain might be something totally different.

If you find yourself in a situation where the battery is indeed draining then check for voltage on the B/Y wire again to see what's going on there. Also, if the voltage drain occurs again then also check the Black/White wire that feeds into the back of the alternator. The B/W wire is part of a two wire plug that also has a White/Black wire.

i'll be sure to check again.....ok i just got the alternator check and it was really bad.....it got really hot just after the test....so if its the alternator, will it drain the battery if the car is park overnight?

Good question and I wish I knew for certain but if you were to remove the three wires connected to the alternator and you were to witness no drain on the battery over time thereafter then you have your answer.

thanks i'll give a shot....

battery draw
 

here is a very simple way to test for battery draw. All you need is a 12 volt test light, disconnect the negative battery lead and put the test light between the battery and the disconnected lead. If the tester lights up you have current draw, the brighter the light the more the draw. Start by removing the fuse for the stereo memory. if the light goes out it is normal is it stays on continue to pull fuses until the light goes out. this is the source of the battery draw.If the light stays lit with all the fuses pulled start looking for other consumers, like the alternator and starter that are HOT all the time. Once you find the source of the draw.................FIX IT.
hope this helps

thanks i'll give it a shot......now that you mention it, the alternator does seems to be very hot.....you can't touch it with your hands at all.....when i take it for testing i have to use a rag to cover it so it won't burn my hand.....could that be the problem? they did say it was bad...

ok, it seems like it was my alternator that was at fault.....i unplug that wire that bolt on top of the alternator and leave it overngiht.....just check it now and voltage seems to be the same so i'll look into buying a new one and see if that drain is gone.......thanks lot guys

Same problem-grounding?
 

I was having this same problem. I never did figure out what was causing it. Altnator tested good and I rebuilt the starter. The problem went away before I could figure out what it was. Can the grounding cause this problem? I have noticed most of the grounds on my car are either crappy or disconnected. "Were" not "are" I have since fixed the ones I have found

Just a tip: don't buy the cheapest reman alternator you can find, and consider having it tested before installing it. There are cheap alternators available through some auto parts stores that can often be bad right out of the box. A higher-end reman from somewhere like NAPA or direct from Mazda will be worth it in the long run.

As long as the main ground to the transmission bell housing/starter bolt is in place & in decent shape, the alternator will be grounded properly through the engine block.

[QUOTE=RotaryRocket88;10095486]Just a tip: don't buy the cheapest reman alternator you can find, and consider having it tested before installing it. There are cheap alternators available through some auto parts stores that can often be bad right out of the box. A higher-end reman from somewhere like NAPA or direct from Mazda will be worth it in the long run.



so what are you guys recommanding for a better and more powerful one without much modification or it is the stock better?

i don't think it was my ground.....but now that you mention it....i did had a wire that i can't figure out where it goes.....its a wire that was wrap with the one that goes to bolt on the top of the alternator, but it was under the oil filter and it had a small sqaure with a ring on it.....i think its a ground but can't figur out where it goes......anyone know where it goes?

It's called a "condenser" and its either for the oil gauge or tach (there is one for each). It's a capacitor and it supposed to regulate the flow of voltage to the respective guages. Many people have their's disconnected, but if you want to refasten it all it needs is to be bolted to metal that will suit as a ground.

so it doesn't really matter where it goes? is that why my tach doesn't work? i mean now i got it to work but i think i might've got it wrong....here's how i do it, you know that female plug at the leading coil and the trailing coil, i just connect those two to make it work......so if that condenser is for my tach then all i have to do is remove that wire i put in and reconnect that ground to make my tach work? yea i know it kinda dumb going through all the trouble, but i just want to keep it as stock as possible except for the intake and exhaust.....

The condenser is there as an element of protection to the tach as opposed to making it work versus not work.

i see...so i check it yesterday and found that the one for my tach is still bolt on to the trailing coil, so that one must be for the oil gauge right? but it weird if its for the oil gauge and is not ground how come my oil still work and not my tach (before i connect the wired from the leading coil to the trailing coil).....