Anyone know about 1990s mazda miatas?

[zsiiKWaRRiorz]

Im wondering if someone could diagnose an electrical an problem.

here is a post i made from a different site explaining everything:

Ok, so i got a 1991 miata a couple of days ago. its having a problem charging the battery while driving. it has a new alternator showing 12.3 or so volts on idle. and it would start out driving good, but then after a while, the charge light would come on, and the air bag light would start blinking. (amount of time/ distance would vary). Upon cutting the car off, it would not start again until recharging the battery. we did a little research and found out that the ignition switch can be the cause, so we removed it and cleaned it. after reinstalling it, took it for a test drive, and those same to lights came on. when we got it home, it would not start. we've ordered a new switch, and are looking into getting the alternator replaced. any suggestions, ideas, or other possible solutions?

also, if anyone can help with this second problem: it makes an odd sound when moving backwards, even if its just rolling a little on a hill before you pull off. it sounds kind of like the lugs of a tire scrubbing the wheel well when turning tires that are too large too far. also, it only does it on the driver rear wheel.

 

[Zastava]

Sounds like bad ground/disrupted ground.. scraping could be 1 bad caliper...of course. Ita just an educated guess. Nothing beats a live diagnosis

 

[loadmyown]

If it is only charging 12.3 volts while running, I would say the alternator is bad, should be around 14 volts running.

 

[shadowchaser59]

when the battery is fully charged. start it up an remove the positive battery cable if it dies then the alternator is not charging. if it does stay running then it's charging. take a oms meter and check to see how much it's charging while the battery cable off if it stay's running. the built in regulator in the alternator could be the problem if it's not charging but I'd just replace it. most part's stores can check it if you take it off and take it to them also. the reason the light's come on is low voltage to the computer.
the scrubbing on the driver's rear is more than likely a brake shoe scrubbing if it has drum breaks. a spring could have come off or just plan worn out. if disk breaks then it's past the pad censer and the metal of the pad's scrubbing the rotor.
hope this help's a bit

 

[2010rjd]

when the battery is fully charged. start it up an remove the positive battery cable if it dies then the alternator is not charging. if it does stay running then it's charging. take a oms meter and check to see how much it's charging while the battery cable off if it stay's running. the built in regulator in the alternator could be the problem if it's not charging but I'd just replace it. most part's stores can check it if you take it off and take it to them also. the reason the light's come on is low voltage to the computer.
the scrubbing on the driver's rear is more than likely a brake shoe scrubbing if it has drum breaks. a spring could have come off or just plan worn out. if disk breaks then it's past the pad censer and the metal of the pad's scrubbing the rotor.
hope this help's a bit

Uhhh Miatas dont have drum 'breaks'...they have disc brakes.
The rears adjusted with an allen wrench from the back side.
If a slider is not properly lubed and/or sticking it could cause the scrubbing issue as well.

As to the other issue...DO NOT pull the battery cable when it is running.
That might work on your 60s Chevy but on a Miata can cause other issues.
I would replace the alternator. If you need a good used one PM me...or for any other used parts.
Failing that I'd be looking at grounds. Its likely one of those two things.

 

[Old_School]

If it is only charging 12.3 volts while running, I would say the alternator is bad, should be around 14 volts running.

^^^^^^ This. With engine off, the resting voltage should be 12-12.5v. With engine running. You should see 13.5-13.8v across battery.

Of course, a shorted cell in the battery may cause your voltages to read low. Has the battery been tested?

 

[zsiiKWaRRiorz]

Thanks all for your input. we are going to get the previous owner to swap out the alternator (lifetime warranty) and see if replacing the ignition switch will help, if not, we can always return it. as well as checking the left rear caliper and the grounds.

 

[Brandon031]

Check your battery terminals they sometimes can cause the problem
Also get the little fabric terminal protector things for 2.99 they help with corrosion

 

[Allsmiles]

Go and check on this site and see if anything sounds like your issue. If not, post up and you should get a response quick. You can also find out if anything else for that year needs to be checked.
http://forum.miata.net/vb/

I drive an 08 6MT GT and have gotten good advice there.

 

[zsiiKWaRRiorz]

got the new ignition switch in today. It fixed the problems with the radio cutting out (i guess i didn't include that bit of info, things would cut out intermittently for no apparent reason) , now we just need to get the alternator out and get the previous owner to swap it out for another. He got it from auto zone, so its almost certainly a re-manufactured one. Hopefully, the next one he gets will charge at the correct 14. something volts.