Electrical Issue, Lights dimming ... help?
 

So i decided to take the turbo miata out for my 2x a week pizza delivery job since I just put the final coat of brightside black and all the trim is back on. Car was running pretty well overall and was damn fast still even though I dropped it down to wastegate 6 - 7 psi to prevent pinging in the heat. Anyways, when it got dark out and I turned on the headlights, I noticed they were pulsing a bit. Then, I cruised around 3k rpm and noticed that the car is hesitating very very slightly everytime the lights would dim maybe every half second or so and resembled the feel of cruising too lean ... currently I am around 16:1 for cruise, but that doesnt seem too lean.

Anybody have any suggestions on where to look? I know I should have taken a look at my voltage in Megatune, but did not.

Edit, just looked at a recent datalog and it recorded a pretty steady voltage of 13.3-13.5 with a spike up to 14.4 for a split second

First thing I was gonna say was to look at a datalog to see if you're having problems with resets or something else in your tune. That voltage seems good and if MT was reading a constant voltage I'm not sure what would cause your problem. Might be worth a try to get a little richer cruise though a few using MS are doing fine with 16 i believe, reaping the benefits of a cooler running engine.

I think Ill take it out again to record the voltage with the lights on and see if that changes anything. I am a bit worried about the alternator as the chasis had 240k miles when I purchased it and the alternator was transfered so basically has an unknown number of miles

That's going to be your best bet, maybe a chassis to block ground came loose or needs cleaning, or the connection at the battery could be flaky as well. A new datalog should reveal something though if the problem reoccurs.

+1 for MS MLV to the rescue. :D

Gut feel says.... alt on the way out.... You might want to check your battery voltage with your car at idle, and see if it's getting 14.4 at the battery.

+1 on the grounds too.... Electrical stuff can be a bitch. I found out the other night why my fogs were going out under braking.... There was the wire for the dash lights, that I spliced into to control the relay for the fogs. The original harness wire was "breaking" so.... when I lost the interior lights, I went lookin' around. Found the busted wire.... I figure it was hanging down, just enough, that my feet were catching it slightly under braking... so it was loosing the connection to the relay -- fogs would go out..... Since I repaired the connection, everything is good again...

But a datalog with the lights on would definately help see if it's getting a voltage dip.

Dave,

Have my car 7 years now. Your problem i had 4 6years... After that:

On mine the voltage stayed at 14.4 and slowly decreaced to 13.6.(link ecu display)
The car would then shut down on itself ... And leaving me with a dead battery.
Charged battery gives no problems. remove the battery from system also no problem... removed alternator to run on battery also no problem...It had me guessing for a couple off thays.


So the alternater still seemed to work, but didn't charge at all.
Strang thing was it was going out right after the 1.6 to 1.8 swap...
Still don't understand.

so you are saying the alternator was the issue in your case and replacing it fixed the issue?

Since then my headlights stopped flickering, maybe the 1.8 dynamo has something to do with it...
But it worked 6 years...so don't worry...maybe you have 6 more years to go...

Well I took my Alternator out and had it tested at Kragen and it failed, so the question now is where to get a quality replacement for a decent price? Anybody?

well screw you guys, im just gonna go with the $105 Autolite remanufactured unit from Kragen then. It at least has a "limited" lifetime warranty so i guess that makes me feel better about it. I am hoping this is the cure for my voltage irregularities as that would make the car much more daily drivable for me ... and I might even get around to fixing up the interior if I drive it more. There were cobwebs forming when I jumped in today :)

ewww cobwebs. lifetime warranty isnt a bad thing its just an alternator it should be fine no matter where you get it

I say buy the local one or whatever. Doesn't matter where it comes from long as it's on warranty. They usually come from the same places anyway, so get what's fast and save the receipt so you get back on the road without electrical probs, even if you saved a little more money(not likely) is it worth your time to save a couple dollars.