I was driving to go get some gas last week and when I went to start the car up and leave the gas station my battery was dead. and it was fully charged when I left so I had to have someone jump me and on the ride home the car would berly pull it self along it had no power,and the volt gauge only read 10volts.by the time I got to the hill before my house I berly made it up the hill. and when I got home and shut off the car the battery was dead again.and if I disconect the battery when the car is running it will stall.could this be a bad altornater and if it is would a bad altornater be why my car had berly any power.

 

Yep. SOunds like an alternator

 

Might be the battery with a bad cell. Charge it up again and have a friend follow you to the local Autozone/Advance Auto type store. They'll test the system for free.

 

I'm agreeing that it is the alt.

 

The alternator has a Black cable bolted to it. This cable is the output wire. W/the car idling the voltage should be 14 volts or so. If it is reading 10 volts or so then is needs replacing.

 

I just put the new altornater on and its still not puting out mor then 12.4 volts.could it be a bad ground somewhere or somthing what should I check next.

 

Are you relying on the voltage gauge for this reading, which could be inaccurate, or are you measuring the voltage off of the Black output wire? Also, make sure that the two wire plug in the back has the B/W wire on top of the W/B wire. Does the B/W wire have battery voltage on it w/key to on (plug can be disconnected for this test). Does the W/B wire have 12 volts as well w/key to on and plug removed.

 

Im testing it with a volt meter on the out put wire on top of the altornater and the battery negitive post and the battery positive and negitive posts I forget what each gives me but they both give about the same reading around 12.4 volts this is all with the engine running.Its dark out now so I will test that plug tomarow and what does that plug behind the altornater do exactly.

 

the b/w wire puts out 12.4 volts with the key on the w/b puts out 11.7 volts what does that mean

 

Does the voltage created by the alternator, read at the volt gauge, change if you rev the car above 3k rpm? Another test that is important is to measure the voltage w/key to on on the W/B wire but the plug needs to be connected to the alternator for this test. This is rather hard to do so you either need a paper clip to stick into the back of the W/B wire to take a reading from or perhaps pricking the wire w/a pin and take the voltage measurement from the pin. Under either case the voltage should be 1 to 3 volts. The alternator excites itself when the voltage reads between 1 to 3 volts and w/o this excitation the alternator will not put out the necessary voltage. And your problem might also be a case of a bad alternator even though it is new and this occurs at an alarming high frequency. Read through the link provided and pay special attention to the posts written by "HAILERS" as he is fully knowledgeable of alternators and other things electrical.

https://www.rx7club.com/showthread.p...rnator+hailers

 

Well the engine isnt broken in yet so I dont really go above 3000rpm to no if it changes volts but I can probably take it up to 3000 tomarow to see if it changes. I will test that wire tomarow to see if its puting out 1 to 3 volts and if it dosnt then what would be wrong with it to make it not put out the volts it needs to like how would I fix it. I also plane on cleaning up some grounds as well like starter ground, battery ground, and the one under rear coil pack.

 

If the B/W and W/B wires check out then either the regulator or diodes in the alternator are problematic. If the alternator is new as in purcgased from an auto supply store then return it for another. Also make sure the alternator belt is of sufficient tightness as a loose belt could contribute to a lower than normal output. Alternators supplied by NAPA are usually the most reliable.

 

ok I tested the wires with a paper clip the w/b wire reads 1.7 volts the b/w wire reads 12volts so I gess that means there ok. so what the brand new altornater I just bought could be bad is that what your saying . should I have it tested at auto zone or will thay just tell me its good if its puting out 12ish volts coz thats what they said about my old altornater,and if I do end up replacing it for another altornater whats the most reliabul brand that I should get

 

An alternator upgrade should be the first modification for every new FC owner.

PM Japan2LA about a FD alternator and pulley. Pretty sure you know how to use the search function (lots of how-tos on this), and will easily find that it bolts right on in place of the stock alternator. You'll need a nut and bolt for the adjuster strap end and will require some minor wiring. It's a piece of cake if you get a pigtail, but isn't too difficult without one. If memory serves, it uses 0.187" quick disconnect tabs, available at Lowes or Home Depot in a multipack for $2. Might be 0.110" ones, but those are included in the same pack too.

Follow the wiring diagram in my gallery to the letter, using 4 gauge for the output cable and you'll be all set. It will need self-excited (rev to 3000rpm), but will fix your car's issues.

Optional, but highly recommended:
I wouldn't leave the original output cable hanging there, it would be a fire hazard if it touched anything metal. Would be wise to de-loom it from the Engine Harness and snip it off where it merges into another cable between the fuse panel and battery. When you do this, insulate the bare wire in red tape so you don't forget it goes to the battery's positive terminal.

PM me if you need help with it.

 

 

ok ry I looked at the wireing diagram in your albume so basicly I need to run the w/b wire to L then run a wire going from S to the egi fuse then run a 4 gauge wire to the battery positive from the altornater output. what do I do with the b/w wire or is it just left alone, and where exactly do I run the wire going from s like under the fuse block under the egi fuse or dose it matter.

 

Check your battery terminals for corrosion.

 

and what do you mean it will need self exited rev to 3000rpm?

 

The unused B/W wire on the alternator plug is left alone. The S terminal wire will be connected to the WHITE wire that goes under the fuse block to the EGI fuse. I used a T-tap for this as it was handy at the time.

When you first start the car up, your voltmeter will read about 12v as the alternator is still "asleep". Revving it to 3000 or so rpm will excite it (wake it up) and it will read the proper 13.5-15.0v then. Not really sure why does this, but my Taurus alternator acts the same way. There's an explanation somewhere in the second generation section.

If you haven't read the Second Generation FAQ, you really should. Many of your questions will be answered there.

 

so do I have to splice the wire coming from s in to the white wire. like is that the idea

 

Yes, you are correct. Also, just a bit of friendly advice, but it would help to not use the word "like" as you did in the previous post. Same thing goes for omitting a question mark. I'm not a grammar ****, just aiming for ease of understanding what you're saying. It's somewhat of an unwritten rule here.

 

I agree with SgtBlue. If you have replaced your alternator already, I would have the battery tested. Especially if you had your alternator already tested and it tested good.

 

Just because an alternator tests good on the machine at Autozone doesn't necessarily mean that it is good. I've seen two alternators test good but were DOA when installed. Mind you, it was on a Dodge Neon, but this is why I swear by the voltage test at the battery terminals mentioned in the Second Generation FAQ.

Not 100% sure about the battery, but a voltage test would get sideways-FC in the right direction. Approximately 12.6v is normal for a fully charged battery, while one with a bad cell would read significantly less.

Sideways-FC, if you don't already have a meter, pick one up at Harbor Freight today, on sale for $5. You'll have the quickest, most accurate diagnosis of the car's electrical woes and will save yourself from Autozone's recycled alternator trap.

http://www.harborfreight.com/7-funct...ter-90899.html

Once you've got the diagnosis, I'd still suggest getting a FD alternator and pulley from Japan2LA. It may only be 30 amps more, but that makes the alternator not work as hard as before so it will last much longer. This is why it's referred to as a reliability upgrade.

 

I have a harbor fraight meter, yea the altornater puts out 12.4 volts I dont know why its not puting out what it should I think I will up grade to an fd altornater.

 

You need to make sure your battery is fully charged before you rely on the readings. It needs to be deep charged if it was drained to below 10v and driven home on without an alt.