An Old Driver but a newbie in Miata
 

Greetings,

A friend of mine was relocated to Huston (we live in Washington DC Metropolitan area) and he did not want to take his Miata 1994. My son (19 years college student in Baltimore) was searching for his first car. This was an opportunity we could not miss. After some lobbying with my wife, we finally bought the Miata, that my son and I will definitely expect to enjoy !!!.

Two months later, the car is still at home with me. I don't want my son to take it to college yet since I have not been able to resolve an intermittent problem with the electric system (battery/alternator/regulator/sensors ??). At the beginning, the car was working fine, but recently, the engine shuts off and the only way to make it work is to jump a charge from another car.

I don't have any experience with Miatas, however I am willing to learn and see if I can fix this issue. I am glad to become a member of this forum and thank you in advance for your kind support.

Manuel

(Patriarca)

When the car dies, is the battery light in the gauge cluster on?
Do your headlights dim before it dies?
It sounds like your alternator is toast.
All you need to change it are a few wrenches or sockets.

Specifics on my problem
 

Dear Monk,
Thanks for your reply. This is what I have been noticing about my problem. Your advice is highly appreciated.
Regards,

ELECTRICAL PROBLEMS WITH MIATA 1994
Background
My friend, the previous and only owner, told me that he had some issues with the battery. That the battery was being discharged with no apparent reason and the engine shuts off.
He took it the car for inspection on 07/15 – Diagnostic – Battery was low, was recharged, everything seemed to be working fine. If more problems appear, the mechanic told my friend to bring it back for further testing.
A year back (09/14) my friend bought a new battery in Advance Auto Parts (AAP).

1st Event
Morning: Greenbelt to UMBC (23 miles)
UMBC to GB (23 miles)
OK
Night: Greenbelt to Columbia MD, (20 miles)
I had lights on, charging my Mobile and listening to music.
When waiting for my son, I turned the engine off and let the battery switch open to continue charging the mobile for about 15 min.
When my son came out, the engine did not start. We pushed it in reverse and I was able to start it. However, it died again few minutes later. We were still in the parking lot. Then we letting it go downhill and started in 2nd gear. After that, the engine worked perfect.
We were able to return home with lights, I did not use the radio, however.
Next day, the engine started without any problems.
I Took the car to AAP for testing. Diagnosis: Battery seemed OK, only one year old, it was holding the charge, and the alternator was loading fine.

2nd Event
Afternoon: GB to UMBC (23 miles)
OK
Night: UMBC to GB. (23 miles)
Started raining, had lights on, radio and wipers after 1/2 way home.
The ABS light started to light on and off after I passed a step bump. The headlights started to fail and one of the lamps retracted. Still the engine was running, but did not have power. I moved to the shoulder of the highway. After two or three miles, I had to pull since the engine was about to die. I turned all lights off and was able to continue my trip (but without lights).
When I got to the last stop sign before enterning my house complex, I had the courtesy lights on, and the engine did not have any power. I turned them off and engine recovered power. I was able to make it home... uff...
Next day, the car started without any problems.

3rd Event

Night: Home to Shopping Mall (5 miles)
Returning home:
I don’t remember if I had the music on, most probably NO since I knew about the problem.
Right in front of the mall, the ABS light started to light on and the engine die. I tried to push it and start the engine, however the ABS light was ON and the engine died immediately. I was not able to start the car until one person agreed to give us a jump. We let the connection for about ten minutes.
The car started fine after that and we made it home safely.
Next day, the car started without any problems.

4rd Event
Afternoon: GB to Beltsville (10 miles)
OK
Returning home: My son stopped at Home Depot, and he was not able to start the engine anymore (we had the lights on).
We were able to get 3 jumps, however the engine continue dying. The last jump was for about 10 minutes. After that, we were able to go back home safely. Before starting our trip back, we drove the car in the parking lot, assuming the the alternator will be charging the battery. We drove back with NO lights.
Once we arrived home, we tested the lights, AC, radio, and wipers. Surprising, the engine never die. Next day, the engine started without any problems.

Next day I took the car for testing again to AAP, the battery checked OK, but low in charge. They recharged it for 1/2 hr and run another test. This time, the test indicated that the alternator was NOT charging.

The battery is still under warranty, however APP cannot replace it. They told me that I need to check for other electrical problems such as the alternator/regulator.

Please let me know if you need more information.
Thanks

Yes, the lights deem off, including the radio clock light. I am not sure about the battery light. What I noticed is that seems to be an indication that the engine is going to die when the ABS light starts lightining, very soft at the beginning then solid ON.
One more piece of info, the alternator was changed in 2007, but the oddometer shows that It was driven less than 8,000 mile up to day. (59,000 then, 67,000 now)

It still sounds like the alternator to me.
Change it, and you should be good to go.
If you buy a new one from the autoparts store, make sure you have the old one out first so you don't have to return later to get your core deposit back.

Sounds like a loose wire, probably a bad ground somewhere is my guess. I just read the alternator failed a test. I would inspect all the wiring between the alternator and the battery, make sure it's all clean/tight connections. If it all looks ok, then I'd replace the alternator.

I will, thanks. I read there are two types of alternators, any recomendation ?

Welcome, Patriarca!

I have done further testing and noticed that the Alternator chargers (14. x Volts measured at the battery terminals) when the Battery bulb lights (deem) in the dashboard at the moment of starting the engine. If the Battery bulb does not light, my readings indicate the alternator is not charging. I was sure that the battery was fully charged. I also noticed that at the beginning, the reading was going above 15 V while I heard a squeaking noise. Few seconds later, the reading went back to 14.x Volts. Any tips ?

Sir,

Alternators are complex devices and have multiple failure modes. They may generate no power, too much power, pulsing power, may fail only when hot, may only fail under a heavy load, may have a bearing failure, and more. My advice to you is to remove the alternator and take it to your AAP and have them do something called a "bench test". They will put the alternator on a machine and hook wires to it then spin it and put in under a load. The results will be obvious and you may proceed from there.

Check your grounds, and then change the alternator.
You need a few 15mm wrenches, a 10mm socket and about 10 minutes.

14mm and 12mm on the NA8.

Aditivo al info
 

One more thing: in the Inside left kick panel fuse box, I discovered that the slot for the dashboard warning lights had a 15A fuse instead of the 10A fuse according to the wiring diagrams. Also, the Air Bag slot was empty, however I tried to install the 15 A fuse but it is not holding, like there is no connector underneath ( I also has the ABag light sending me the code 1 and 3.
Would this de also a source of the problem ?

Thanks
 

Thanks

Let us know what the bench test results are.

Thanks all for your comments. I am happy to report that the mechanic diagnosed the problem in the Alternator. I understand that the regulator is integrated within the Alternator. We changed it and so far I have not had any issues. The Battery warning light in the dashboard lights up when I start the engine. After that, the light goes off. I measured the voltage while the engine is running and I am getting 14.x Volts.
I still have some other questions regarding the Air Bags, the Antitheft system. Where should I go in this community for those topics ?
Thanks again for your support.

I have also became a member of the miata.net forum. Are you connected somehow ?
Thanks

Your airbag/antitheft questions can be answered here in this thread more than likely. :bigtu:

And no, not connected :hatecat: