Our 94 enduro car has started eating alternators just about every endurance race. We have tried used OEM Mitsubishi, and new Denso alternators with the same result. I am thinking there is some intermittent issue with the signal wire coming back to the alternator for the internal regulator, so we are thinking about running the signal wire directly off of the alternator main to the S terminal that is normally the W/G wire. Does the warning light (L) W/B need to be hooked up to function properly?

I am at my wits end trying to figure this out and this seems like the simplest solution if it is a viable option. Can any give input as to how they would go about this?

 

I have mine hooked up locally at the alt, ugly style.
12v to S, 12v through a small bulb to L.

You can replace the bulb with a suitable resistor, but it's a good warning that you left the main switch on (or you will drain the battery before the next race).

No clue about the 94 harness, but I think you'll still be able to use the cluster bulb as the bulb in this situation.
What does the S terminal go to on a 94?

 

So you do need to have the light wire hooked up for the alternator to function properly? I have heard mixed things on that, but it would have sense if it did and we were having this trouble as our dash has been removed along included the warning lamp circuit.

 

Can you run a non-stock alternator? I find that all the mitsu style alternators suck. Better luck finding a denso style one like that Geo tracker, nearly bolt in, find my write up in the ultra light alternators thread or my build thread.

 

Yes, we can run a non-stock alternator. We have gone through two new Denso miata alternators already. I will take a look into the lightweight alternators thread you mentioned to see what I can get out of it.

Can anyone answer if the battery warning light terminal needs to be connected to make the OE alternator function properly? I am hearing mixed things.

 

Is it the regulator dying?

I blew a couple of regulators on the stock alternator even with an oversized pulley. I'm reving pretty high so I think the heat or charge just cooks them.

Now I run a tiny Suzuki alternator and haven't had issues. It's a two wire alternator so basically the same as early Mazda ones and with a bonus of bring able to pick them and unlimited supply for $30 each from the wrecker.

My other solution was to run a standalone inline regulator.

 

Hey-o! We're not the only ones. Gone through a dozen or so alternators. Some last an hour, some 8-16. We thought it was the ecu
controlled regulating, so we recently switched to na8. Two baxters ones lasted ~1.5 hours, orilleys then lasted 12
and still going strong.

We believe its just over heating and over spun. Remember you get 14+ volts at idle, anything else is wasted. I've contacted garage star about a larger pulley to under drive it, and this weekend we tried a duct from the turn signal to alternator.

Shame really, were WRL winners and would be lucky dog podiums if it weren't for alternator failures.

 

Oh and we only run the 12v supply, no light.

 

I feel like this may be potentially part of our issue. See this post in the light weight alternator thread:
https://www.miataturbo.net/race-prep...2/#post1390418

I think we may actually need to do something with the L terminal to have it function reliably. This goes beyond my expertise, so I would love to defer this to someone who knows more than me on that. I have talked to several people that have had issues with regulators acting up after dash warning bulbs were either disconnected or burnt out.

I know there are diodes in the OE wiring going to the dash, but can I simply attached a bulb inline of a wire going from the alternator output to the L terminal? Again, forgive my ignorance on this.

 

I would want the alternator light working anyways so you have a warning that you've thrown or cut the belt, before the car catastrophically over heats, but thats just me.

 

I plan on putting it back in the car now for that reason, but I am also curious if it is contributing to the issue by not having it in there currently. We will see. I would be very happy if we could stop making so many paper weights out of these things.

 

I really think it's an issue of over spinning, over heating, and poor quality rebuilt units. We ran 12 hours without a light.