Possible alternator issue.
 

So I've had this intermittent issue. Started a couple months ago, but was extremely rare, however it's become much more consistent. I checked the battery and it read 126cca, so it was obviously bad and I replaced it with an interstate. The issue didn't show itself for a couple days, however.... I've attached a video so you can see when I accelerate the lights come on, and when I allow it to even out some the lights either dim or go off. If I accelerate and keep accelerating then the light comes back on and now the abs light flashes. Before I buy a new alternator, I'd like to see if anyone else has had similar issues, or if I'm looking in the wrong place and need to look for an issue in the wiring.

http://youtu.be/I_AJlxz098c

I can't figure out how to post a video, if someone could help I'd really appreciate it.

I had a similar problem, I had a bad battery so replaced that and pretty much the same results as you are getting...turns out the alternator was bad, which probably actually made the battery go bad. When you rev the engine past a certain rpm the alternator charges the battery regardless if the control unit is bad. For me I pricked the wires going from the ecu to the alternator, the excitation voltage I believe is supposed to be around ~1v was showing like 5v...I replaced the alternator and have yet to have a problem...also in all my troubleshooting I ended up getting a alternator from autozone which died a week later, so I took it back and went and picked one up from advanced and it's worked amazingly.

I would recommend checking the excitation voltage, and make sure your alternator is grounded good...but definitely looks like a bad alternator.

btw the battery light comes on when the voltage is below like ~14volts (when the alternator isn't working) so while you'll beable to drive around for awhile since you have a new battery. but you'll want to replace that alternator soon before you drain your battery completely.

Check all the alternator connections and belt. What voltage are you getting at idol/rev? Easy enough to pull out and take to get tested before laying down $$ on a Mazda replacement.

Some signs of low voltage are all the warning lights come on, engine hard/impossible to start and the air pump clicking on and off.

So I checked the alternator today. Idle its around 13.7 volts and under acceleration or at 3k rpms its at 13.9. I'm no rocket scientist but I thought that an alternator should be pushing closer to 14.5. With all of this being said, it wasn't acting up today, and the charge light wasn't coming on. So if it is an issue with a diode like I suspect, then I don't think ill see the horrendous readings until I get it to act up and test it then.

Actually 13.7 volts may not be that bad if the battery is already charged. If you don't have any extra load on the car (audio AMP, lights on, AC, cooling fan, etc.) the voltage shouldn't be rising at 3K RPM. To me that's a sign that the alternator is on the way out.

If the battery is discharged (it is a bit right after you start up) then the voltage should be over 14. Alternators change their voltage based on load, charge state of the battery and temp. Was the alternator hot when you checked it today? It may act fine when cold and give out when hot.

I'll give mine a test when I get home today. I do know that my lights dim a bit when idling. These alternators aren't the strongest ones out there.

Well according to my workshop manual its saying the alternator should be at 14.1-14.7 at idle. When I checked the voltage at the battery it was like 13.5, I should have wrote down all my numbers, but I did it as I was leaving work. I'm just going to swap it out and hope it solves it. They're not too expensive or difficult to get out.

That's true ... they aren't pricey or difficult. If it's the original alternator it's 20 years old and bound to fail sooner or later.

OK, so I kept an eye on my commander (PFC) on the way home. The voltage started out at 14.2 and then dropped to 13.9 half way home (5 miles) and then hit 13.7 a few miles later. It stayed there for the last couple of miles.

When I've left the ignition on for a bit to tune the car I've noticed that it will shoot up higher initially. Say 14.5v.

Bottom line 13.7 is normal if the battery is charged and it's about 75F outside. Lower temps would push the final voltage (when the battery is topped off and charged) higher. Higher temps would push it lower. Thought I don't think that it would push it too much lower. Maybe 13.5 volts if it crossed 100F.

I'm assuming that in 93-95 Mazda's alternators had temperature compensation but I would be surprised if they didn't ...

Let us know if the replacement alternator solves the problem.

Good info here;
https://www.rx7club.com/showthread.p...hlight=voltage

Read post #9

If the car is hot (has been running and up to temps) the fans should be
on, and the voltage will read 13.3 or above, at idle. This is normal.
The only time I see above 14 volts, the car is cold and has just been started.

Hmm... So I may have to dig through the wiring and try to find a fuse or possible wire issue. My one concern is that I wasn't able to test the alternator when the light was on. It's an issue under load, because I can even out and it's not on. I'm beginning to think it could be a ground issue somewhere? I did buy a new alternator for 105 new, and I'll be installing it on my next day off. I'll keep you updated.

An update on this, sorry for the delay, but soo much stuff is going on in my life and it's been a pain in the ass to get time to actually work on the car. I went ahead and ordered an alternator, and installed it today. With the limited tools I have at my disposal, it was a royal pain in the ass. After some perserverance I finally got it in there. I did break 2 hoses though, 1 vacuum and 1 that sits right over where the alternator bolts down (that one sorta disintegrated). I switched the 1 small vacuum hose with another one near it, same size and all, one was a tad bit longer, but both went on no problem, and I was able to get everything back together and double and triple checked all the lines to make sure everything was together. I let the car warm up, and decided to take it down the road. No charge light! No warning lights whatsoever, HOWEVER, my boost if I hold the about 60% throttle it boosts to 12psi, but if I go like 80-100% throttle, it goes up to 15psi (it may keep climbing but I'm too much of a p---y to stay on it and see where/if it stops). Could swapping those 2 small vacuum lines have caused this? Or could I have possibly missed something? I plan on getting back into it this weekend and tearing everything back down. I'm thinking maybe I put too much weight on something and a hose came loose somewhere. Any input would be GREATLY appreciated.

I took everything apart again today, well not quite everything, but I found where one of the vacuum hoses to the boost chamber was split in half. I'm assuming that's what's causing the issue I'm having, and I've already got some hose on order, waiting to be delivered.

I installed the broken hose and its not out of control however its still boosting to 15psi. I guess ill just keep digging for more hoses, I suppose I could have leaned on something and not realized it split. An alternator should have little to nothing to do with the boost. So I'm a little stuck.

I just installed a Triumph air temp sensor in my stock location. In the process I managed to snap a nipple off of a solenoid. When replacing the solenoid I dropped the nut from my efini y-pipe down in the turbo area.

This car down not reward one who rushes. This sort of things happens to all of us. Look at what I did and I've had more than enough experience to know better.

Anyway, grab one of the color coded vacuum hose diagram and patiently go over things in the front of the rat's nest. You'll find it.

Well Mr. Paventi, I may have found the issue. I haven't gone through EVERYTHING yet with a proper diagram, but I've just been so stumped, and so upset with myself for possibly breaking something. I did notice 2 connections mounted on the UIM, the one on the left (in my workshop manual its called the duty solenoid valve) has 2 vacuum nipples and the one on the right has just the one vacuum connection. I snapped the upper nipple on the left solenoid. I suppose I'll be calling Mazda tomorrow and hopefully they can find one, or if anyone here possibly has one, I'm all ears!

I agree ... I think that you have it.

You might try to carefully superglue the nipple back on. If it holds it will tide you over for a while.

I'm guessing from your trader score that you know about the 3rd gen for sale section? Check it, if your in a hurry post in the wanted to buy section. If you're in more of a hurry I'll bet Mazda has them. Do you know about Ray and Malloy Mazda? His prices are the best and he knows RX7s.

I just received the y-pipe nut that I dropped from a forum member yesterday ... my car will be back together tomorrow. Well, it runs now, just with a nasty boost leak.

I was thinking of either a super glue or some sort of epoxy. But I'll be replacing it this week for sure, so I may just leave it be until I replace it. Best of luck with yours, but you're not concerned with where that bolt of yours ended up? I'd start hearing things until I found that bolt, or it would forever bug me.

My alternator had a similar issue. It would work fine then I would rev or downshift and the lights would come on. I narrowed it down to the connector that plugs into the alternator. I could duplicate the issue in the garage with the hood up by reving the engine. I checked the connector it was fine and then finally pulled the alternator. I took that apart and found the solder that connects to that plug inside the alternator had cracked. So it was an intermittent short caused by engine movement/revs. I soldered it back up and put the alternaor back together. Remember when assembling the alternator there are tiny holes to put a toothpick or small piece of wire in to hold the brushes out until the shaft is in place.

I went ahead and pulled the duty control solenoid from under the UIM, took roughly 5 minutes, I went ahead and marked all the vacuum lines to ensure they went back into the same position. I super glued the nipple back on, let it sit up for an hour, then added more super glue, just wanted to make sure I really coated it. Vehicle now has perfect boost pattern, 10-8-10. I'm still replacing the solenoid on tuesday, regardless.

I put everything back together yesterday with the bolt that I ordered.

This car is a constant challenge to keep quiet. Well ... challenge to remove the next rattle. I just pulled my wing and removed some plastic bits that were rattling around inside. As long as the nut doesn't fall inside of the engine's intake I'm happy. :lol:

Glad to hear that your boost pattern is back. Once you have the new solenoid, save the old as a spare.