RX8Club.com - Alternator Good (Says Tech) but Charging CEL still on

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Alternator Good (Says Tech) but Charging CEL still on

how old is your battery?
The problem is not with the AP

If your alternator is not putting out 13+ volts during operation then it has issues. Sounds like the internal voltage regulator has gone bad. Or the alternator is just worn out. I would get a new alternator.
Or take it back to the company that fixed it and show them what your seeing on the Cobb Accessport.

Input below:

Quote:

Originally Posted by RX8Prodigy (Post 2884784)

So I've read a lot of posts regarding the alternator and charging system, most of which point to the alternator and then the others say "Get it checked at nearest dealer".

Well I've checked and fixed my alternator, which was not holding a charge and running down my battery. My car usually runs at 14+ V (says my AP) but now, after repairing the alternator, it is running at below 11V (well today it is at 10 and below after starting...it pretty much drops to 8-9 during crank).

I have a 2004 6MT RX8 which has been working perfectly (no starting problems, no electrical issues, not stalling, just PERFECT) and has 93000 miles on it (but is in perfect condition and I have had no problems).

Anyway, to my questions:

1. If my alternator is indeed good (1 shop fixed it and the 2nd shop verified that it was good) what is causing my charging system to still have problems? (Computer issues?)

-It could possibly be a weakness in the wiring harness, if in fact the voltage reading at the alternator is proper.

2. Can spark plugs have anything to do with this? (however, engine does run very smooth with the low charge)

-No

3. I've even jump started the car and at start (with the wires still hooked up) it was still pushing the low voltage.

-n/a

4. So if the alternator is working, and is not pushing out the correct voltage it should, what could be causing that?

-The alternator is either working properly or it isn't. If it's not putting out 13.5-14.5v then it's not working properly. Again, if voltage measurements at the alternator are ok, check the downstream voltage (at the battery).

5. I really need some help and advise on this one. I've read a lot of posts the last few days about the alternator/charging system issue, but none really gives much tech help for a charging problem when the alternator is GOOD.

-same response as 4.

6. One last question, can the AP cause such a problem with the computer where it causes the computer not to allow the Alternator to produce the correct current? I wonder if I should try to uninstall the AP and see what happens? (I'm afraid to try this with the low voltage)

-No

PLEASE HELP - oh, I live in the Caribbean, so I cannot just drive it to the nearest Mazda dealer (we have none here...well we have one but they would either tell me they will not work on it since I imported it myself or they will simply damage it which is often what they do to cars)...

-Again, check the voltage at the alternator ouput and at the battery with the car running. If there's a discrepancy then you have a wiring harness issue. Although modern wiring harnesses are pretty reliable there's always a chance there's been degradation.

Oh, and of course check the belt tension on the alternator itself. If it's slipping it can't put out it's optimal voltage.

You're able to start/run because you still have 12v via the battery, but if your alternator is putting out less than 13.5v you'll soon deplete it.

HELP HELP HELP!!!

So would any of this mean that my computer has a problem?

i have most likely whatever you need to fix it if you are not under warranty. PM me if you need any help

My battery is about 8 months old. I is the kind you can refill the battery water, which I did...and the voltage went up to about 12.7, with my Charging system CEL still on.

Our Alternator should output around 14.2-8 volts at almost all times.

11? even 8-9 ? The thing is either broken, or your belt tension has a problem.

First check and make sure your belt is tighten correctly. if not check your alternator at the battery post.

oh , AP is NOT the cause.

Alright..........listen up.

As has been stated, once the car is running......the alternator should be putting out right around 14.2 volts.

Two places told you that your alternator is good, so it probably is. You need to start the car and measure the voltage at the battery(not with the AP!!!!). If it's reading 14.2v then it's okay.

I want to tell you this but I'm not sure about your mechanic/technical ability....but........once you get the car started and read that voltage at the battery, if it reads low.............let's say lower than 13.5 volts, then you could CAREFULLY remove the positive leads off the positive side of the battery with the car still running and while still measuring and see if it jumps up to 14.2 volts. If you attempt this, don't let those positive leads come in contact with anything else while they are off the battery and the car is running, or you will be very, very sorry. You kinda need two people to do this.....with one being in the car.

If the voltage does jump back up when those leads are off the battery, the it is your battery and based on what you have said.......I believe you will eventually find out you have a shorted cell in your battery and that is dragging down the alternator voltage.
BTW.......did you know that at the very least, it's supposed to be distilled water that is added? Based on the fact that you saw it get a little better when you just added water........I'll bet you have a shorted cell in the battery.

You need to not rely on the AP for the moment and get under the hood and make these measurements.

Someone tell me I'm wrong after reading what all he has said.

Yep, I did get under the hood and do all the test a while back...before and after the garage "supposedly" fixed the alternator and the problem was not fixed. I even used a BRAND NEW BATTERY to diagnose the problem. I only use the AP as a reference point. The determining factor for me was when I removed the positive terminal and the car died.

The replacement alternator should be here today...and I will install it with my fingers crossed.

Well of course the car died when you removed the positive cable - the vehicle runs off the battery (which the alternator recharges). The alternator has enough voltage to run the vehicle, but not enough current (amperage).

Anyway, basic Ohm's Law aside, most likely it is the alternator, despite the shop having 'fixed' same.

btw: when adjusting the alternator for proper belt tension be careful not to pry on the alternator body itself as it is typically soft metal and might short the windings if warped.

Quote:

Originally Posted by RX8Prodigy (Post 2894245)

Thanks for that tip about prying the alternator body...I have pretty much perfected the art of installation and removal of that alternator, but my first go at it was horrific and I ended up using a jack wrench to pull the alternator out of place (not the smartest thing, but at 12:51am I was not in the mood).

Quote:

Originally Posted by Huey52 (Post 2894261)

I'm calling shenanigans. An alternator is capable of keeping the entire car running by itself. The battery should only be needed for starting. I wouldn't recommend trying to do it on a car with modern electronics (It's a very good way to fry your ECU if everything doesn't go as planned), but I've got co-workers who have started their truck with a battery from another car, pulled the battery out, then drove to the autoparts store to get a new battery for the truck.

If the alternator couldn't power the entire car and then some, you'd end up draining the battery pretty quick. To charge the battery while the car is running the alt will have to put out as many amps as the car is using, and then some more on top of that to charge the battery.

Yep, good catch. I meant "start", not "run." Cold cranking amps related (which btw really relates more to the "locked rotor" electrical inertia of the starter motor than cold temperature).

But as you indicated, not good for all the vehicle's electronics to be run directly off the higher voltage output of the alternator.

Quote:

Originally Posted by Socket7 (Post 2894501)

Got the replacement alternator from Maniac Motors today (via Fedex). Installed it and ALL IS WELL.....on my way back to the two shops to get my money back.

Wow..i'd forgotten my 8 was so swift. My days of driving the company pickup are OVER!!!

Thanks for all the inputs.

Glad to hear all's well and definitely get your money back from those bogus 'alternator repair' shops.

So it was the alternator! Sweet. Glad things are working for you.

Pretty lame that 2 shops couldn't get it right.