The car is an '84 with a 12a

The first problem was on my way home, everything electrical in the car stopped working, but it was still running fine. I went home and replaced the battery with a spare just to eliminate that as a problem and the car started up just fine, everything worked again.

That battery worked for all day the next day, but eventually the same thing happened again with everything electrical not working, or working very slowly. The wipers moving slow, the lights coming up one at a time. This time though the car just died on me entirely. I got a jump, and it worked for a few blocks then died again.

Now as far as I understand this is all pointing towards the alternator, but is there anything else I can check first, I don't exactly have $150 to throw at a new one.

Thanks in advance,

Note: I'm still a rookie at this whole car thing, I just really love driving my RX-7.

 

Have the alternator tested. Most parts stores will do this for free. If bad, try a junkyard for a cheap replacement...

 

Either that, or you have 2 dead batteries.

Putting a 'spare' battery in may last for awhile, but unless it's getting a solid, high-amperage charge regularly, I wouldn't recommend keeping a spare. Plus, putting a NEW battery in will tell you a lot more about what's going on with the charging system.

Alternators work by creating a magnetic field using the current in the battery, and then spinning a stator in the center to generate current. If your battery doesn't have enough juice to create the magnetic field, you're not going to be generating any current through the alternator. In other words, there may be nothing wrong with your alternator other than your batteries (primary and spare) are too weak.

Also, check your alternator belt to be sure it's tight and not excessively worn. Slippage on the belt can result in reduced alternator output.

Good luck, my money's on the battery (all 2 cents of it!)

 

What does the voltmeter show while the car is running? Do any of the warning lights remain lit while the car is running? Both these can tell us more about what is going on.

Easiest solution is to have the battery and alt tested (battery will need to be charged before testing). Most autopart stores will test both free of charge.

 

I took the alternator to Autozone, and it failed miserably. So I called around to some junk yards and all they have is 2nd gen RX-7s, so for now I'm screwed unless I try to convert it to one of the newer alternators.

As far as the 'spare' battery goes, I actually pulled it out of another vehicle just to test my vehicle, even made sure it was fully charged. Just didn't think anyone wanted to know that and summed it up in one word. Learned my lesson there though

None of the lights work at all, including the warning lights, and the voltmeter slowly goes down to 0 from a full charge.

 

They can convert easily, I believe the S4 alternators bolt and plug right in, good upgrade too

I myself run a GM C130 105 amp alt, only needs minor modification to work

 

Yep. The S4 (86-88) alts will drop right in. Get one off a TII if they have one (has more output than the NA one). The S5 ('89-'91) ones will also work with a simple change in the wiring. All of the S5s are 80A. The S4 are 60-70A depending if you get one from an NA or a TII.

 

Sweet, if an S4 drops right in I'm just going to grab one tomorrow. I would upgrade it to a better one, but I'd prefer to have someone with me who knows what they're doing. To paranoid about digging myself a deeper hole since I have no experience with this kind of thing.

 

if you go to a junkyard, be sure to grab the FC alternator spacer and the FC alternator bracket also.

 

...and cut off a few inches of wire and the electrical plug from the car.
http://www.rx7.org/public/altxref.html

 

I actually found an '81 at the junkyard, bolted right in and it appears to be working fine. Huge price difference, only $17 from a U-Pull-It yard.

I jump started it because I had my 100% dead battery in it and the car stayed running instead of slowly dying. The voltmeter is right under 12v, is that good?

 

nope

 

You need to take your battery to Auto Zone or whoever and have then charge and test the battery.

The alternator is not a "Battery charger". It is only there to maintain the system and if you try and recharge your battery with the alternator then there is a good chance also that you will burn it up.

Also if the old battery did not survive and will no longer take a charge then the alternator will not read correctly as you cannot charge a battery with a dead cell in it.

 

Alright, I'll test the battery tomorrow.

I must say thanks for explaining these things to me. Other forums probably would of given up by now.

 

or they would have told you to "SEARCH" LOL