jlee916

I just bought a 90 GTU and the car dies fairly quick. The car turns on and we let it sit and do its thing like warming up for the first few minutes before driving it. I took it for a test drive around the neighborhood/a road that can do 55mph+ and it was all good. After paying and signing the paperwork, I drove down to get gas and was gonna hop on the freeway on home, but my car wouldn't start anymore. I thought it was the oil 'cos it was low, so I bought some and added more in. It still wouldn't turn over, so I asked someone to help give me a jump. Car started right up and I drove down the street and died right before the freeway ramp. I notice that the battery indicator started dropping down towards 8 on the dash before it died; luckily I was able to pull to the side of the road. I noticed all the warning accessory lights are on near the top of the dashboard while I drive.

Long story short, I thought it's the alternator because we tried the "pull off the positive cable on the battery to see if the car still stays on," and it died suddenly. I went to pick-n-pull today and got another alternator. Installed it with another battery and still same thing.

I should've tested the alternators at autozone or oreily's before driving over an hour from my mom's house to install it, but now I gotta wait until the weekend comes before I head back 3 hours to get my car back. I'm gonna have my friend tow it with his truck. As soon as I have it in my driveway, I'll be able to try and figure out what's up with this. Perhaps both alternators are bad, but I want to see if anyone else has any thoughts on this. What else could it be? The engine fires up every time I add a good battery in, but it drains so fast after a couple of minutes of driving around. If I leave it in neutral, it seems to be good.

Aaron Cake

iTrader: (1)

First, no reason to warm up the car before driving it. Just start up, put on seatbelt, drive, then don't beat on it until it has reached operating temp.

NEVER pull off the battery on an EFI equipped car while it is running! The alternator voltage will rise, and the output is very dirty.

It wouldn't surprise me if both alternators were bad. 2nd gen alternators fail fairly often.

satch

iTrader: (1)

With a meter in hand measure the output voltage of the alternator. Use the wire/cable that you pulled off when trying to diagnose your problem (connected to the alternator of course). W/the car running the alternator should be putting out about 14 volts. 14.4 volts to be exact. And if you didn't know, the idiot lights all come on when the alternator is failing as this is the warning sign given.

builder

Best way to eliminate possible problem areas are to test components off of the car. If the battery holds a charge and the alternator tests ok, start looking for bad wiring connections. A bad ground from engine to frame caused voltage problems for me.

boosted516

could be bad grounds sounds right

jlee916

Turns out it was the alternator. Managed to buy one off a member here and drove 3 hours to mount it in. Runs real good!

RotaryEvolution

iTrader: (30)

been doing it since i was a kid and never had a single issue with anything getting cooked.

Aaron Cake

iTrader: (1)

Doesn't mean that it's proper procedure. If you've not fried anything, that's good. But a few years ago when I saw someone perform the exact same test, he fried his Haltech. The datalog showed the voltage up around 25V before it stopped.

RotaryEvolution

iTrader: (30)

yes i know it's risky, i doubt i would do it on an expensive built car with a standalone. but there is probably underlying reasons it shot up so high, usually caused by poor electrical flow through the chassis/engine to begin with.

rtrpowr

i have to agree there is a slight risk but its pretty slim, it might happen but then again you might get struck by lightning too.

Aaron Cake

iTrader: (1)

Well, I've been about 25 feet away from being hit by lightening, so I may have a different perspective than most.

sdblackgloves

haha yea that explains a lot and i sure would not play around with electrical stuff like that if i had the same experience.

but to thread starter good thing you figured out it was the alternator. you could always use a multi meter to check charging voltage to see if its faulty or not.

jlee916

So I got the car back home to my drive way now. I drove it from 3 hours away with a working alternator; I had the alternator tested at autozone and it passed. The car ran fine on the highway and local roads. I even stopped in another city to hangout with my friends and eat before driving 1 hour and 40mins home. The battery meter in my S5 cluster was reading above 12, about 13-ish I'm guessing. I parked my car and the next day, my battery is drained. I had to jump it and the battery reads around 12 again. I drive around a bit to try and charge it up, but it died again the next day when I tried to start it up. It does this everyday with me needing to jump it. I don't see/leave any interiors lights on nor the headlights on.

What should I do to tackle this problem? I thought about swapping my batteries since I have two cars, but I'm afraid I will put myself in a bad situation. I imagine that the s5 will drain my other car's battery, therefore I'll have two dead batteries! Anyways, I also have myself an Equus Innova 3306 digital multimeter. I just need help.

Thanks!

RXSpeed16

iTrader: (41)

Get your battery tested. They don't like being drained all the way. If both the alt and battery are good, something is wired incorrectly and getting power with the key off. Check any non-oem wiring for things that are getting constant power and they need to be changed to switched power (12v only with the key on). Stereo, amp, lighting, fuel pump, electric fans, etc. If you don't see anything obvious, start pulling fuses and measure current across the terminals. Once you identify the circuit, you'll have to inspect the components on that circuit.

satch

iTrader: (1)

You should also think about performing an amperage drain test. You disconnect the negative battery terminal and w/the meter set to measure amps you apply the Red meter lead to the unconnected battery post and the Black meter lead to the disconnected battery cable and see how many amps are being drawn. To do this test you also need to let the car set for a while if you have recently had the key to on as this causes the circuits to draw power and the drawing doesn't immediately stop after turning the key to off as it can take 30 to 60 minutes to completely stop. Also make sure the door is closed so as not to turn the interior lights on.

EOD_RX7

Pulling the terminals on a newer model vehicle while it's running is a bad idea. It can cause all sorts of damage to the electronics, and can cause your airbags to deploy If equIpped of course. Best way to trouble shoot electronic systems is with a multi meter.

jlee916

i brought the battery into autozone to get it tested and charged. within an hour, i was told the battery was no good. i figured since after learning how to use the multimeter, my battery was only holding charge at 8v with car off and 10v with car on before i brought it in. i just took my accord's battery and dropped it into the rx7. everything seems to be really well; all the lights are bright, car starts up with no problem, cluster is bright, currently reading around 13v-14v. i'll report back tomorrow as the car sits over night with it inside.

i hope everything goes well and that it was just a bad battery, so i don't have to spend a whole bunch of money and look for other causes.

builder

A battery drain test costs nothing. Just take a multimeter and connect it between one of the terminals to see if there is a drain.

I had the same problem with a motorcycle years ago, it would eat batteries for no reason. Used the multimeter and found a slight drain, then started tracing it backwards from the battery. The drain stopped at the solenoid, I found out the rubber dust boot was conducting across the terminals! Pitched it in the garbage and had no more troubles.

jlee916

it's been over 12 hours now. the car still starts up perfectly with a 12v-14v reading on the swapped battery. it seems most likely it was a bad battery. i'll leave it in for another day or two just to be sure.

mdfitness704

alternator

jlee916

the alternator i added is a good one. it passed the test at autozone compared to my previous 2.

genefc3

most likely its ur alternator have it check on autoparts store

Panameno

iTrader: (1)

i hope everything works out.