96 alternator voltage dropout
 

I am having a weird alternator (from a 96) issue where the voltage will drop to <11.5V while I am cruising. The first time it happened I cycled power to see if it would reset the regulator or do anything, but my Tunerstudio readout still showed <11.5V and dropping. I tried to shut the engine down and restart again, but it would not restart. Had to coast down and pull to the side of the interstate. Tried to res start it, but now the voltage was down in the 9v range and it would not crank. I cut everything off and popped the hood and trunk to make sure all the battery and alternator connections were ok and did not find any issues. After waiting 5 min I just rolled the car down the hill and popped the clutch which was enough to get it started, but the voltage reading was still in the 9v range. I finally revved it a few times up to 3000-3500 rpm and all of a sudden the voltage jumped up to 13.8V and started working fine.

When this occurred I did not have a substantial load on the alternator, I don’t even think my FM Spal fans were on at the time since I was cruising. I did have my inverter in to power the laptop.

I have been driving the car for a few days now with no similar issues, until this morning. I started noticing that my coolant temp gauge was reading about 5 deg to the left of normal operating temp (after driving for 30 min) and looked at Tunerstudio to see the voltage down in the 10V range again. This time I just pushed the clutch in and revved it a little and it bounced right back up to 14V and remained stable until I got to work. Sounds like a regulator problem to me.

This is my 4th lifetime warrantee swap from Autozone. I just replaced this one back in October, usually I get at least 1-2 years out of them. Luckily I can replace the alternator in less time than it takes me to drive to the store and get a new one. I am getting tired of dealing with these cheap reman alternators and am starting to look for other options.

Looks like a FD 100A alternator is a fairly straight forward drop in solution and does not have the power quality issues of the FC alternator. I read somewhere about the Milenia alternator being an option, but it looks like it has a 3 wire connector instead of the 2 wire connector I have on my 96 alternator. I am assuming this is for external control like the NBs use. I also have a 01 that I am parting out and was wondering if the NB alternators are more robust. If so I might try to get the MS3 to control the NB alternator.
Does anyone recommend any other better reman options for the Miata alternator?

new?

Rosenthal didn't have a new alternator, only remans so I didn't look much further for a new alternator.

even if you go with the rx7 upgrade, you may run into same issue, but itll be a better alternator to use.

I dont like the NB alt, even with a controller.

It looks like I can find the FD alternator for a reasonable price, appears to use the same 2 wire connector and has 100A capacity vs. the 70A automatic alternator I have right now.

Man my autozone alt died after a year as well... It started doing the dropout thing, then it started to overvolt to ~17.5V.... Not too happy with the situation.

Where are you finding the FD alt?

yeah it's pretty much PNP.

You may have to change the lower bolt or run a spacer of sorts, i cant remember anymore.

It did it to me again on the drive home. I hope Autozone will just refund the cost of the alternator since I have had so many issues.

I also had issues in the past where the voltage dropped out on one and another one would charge at like 15.5V intermittantly. Always seems to be regulator related. Must be cheap chinese electronics in there.

Parts store rebuilt alternators are notoriously bad. People often report them already being dead in the box, and having to get multiples before getting a good one is on the verge of considered normal.

I had my stock alternator rebuilt by a local shop for a little over $100 3 or 4 years ago, and haven't had to think about it since.

the problem is they dont replace the regulators when they refurbish them.

Didn't know that, that is just stupid! I wish I could find a replacement regulator and I would do it myself.

keeps them in business doesnt it?