[DaSouthWon]

96 mazda miata, 1.8l, manual trans. My problem seems somewhat simple but I can't seem to pinpoint it. I purchased the car about a year ago and after doing a considerable amount of work to it, it hasn't been driven much. A couple months ago I went to crnk the car after it had been sitting for about 2 months, needless to say I wasn't surprised that I needed to jump it off to get it started. Once cranked I drove it about 30 miles to charge up the battery enough to get it recrankable. When I got it back home I cut it off and tried to restart it immediatly. dim interior lights, weak door buzzer, and a few clicks from the starter were all I got. I repeated the jumping off and drove it some more to see if it corrected the problem. I did this a total of 3 times with the same response. I figured the battery was bad so I ordered a new one (glassmat type). Put the new battery in and it fired right up. Drove it a few times over the week and then it sat. I went to crank it the other day and it was totally dead. Figured parasitic drain. Jumped it off, drove it 60 miles, came home tried to recrank and got nothing. not even dim interior lights. Figured I burned up the alternator trying to recharge the battery so many times. Removed the alternator, disassembled it, everything checked out ok. Did replace brushes and cleaned a few things up while I had it out. Retested after reassembly and the alternator is fine, and was working sufficiently before anything was ever done to it.

Did I just get a bad battery or what else could be up? All cables are tight. Haven't reinstalled the alternator. I know I should have checked a little more in depth before I started changing parts I just figured were worn out. Anyone have any ideas?

This is a glassmat type battery and I do know that it takes a much slower charge to get it up to par. One amp max. Its cold and rainy out, one of the reasons I just replaced parts rather than digging in.

 

[T-bucket23]

I would have the alternator tested. If it checks out then you probably have a bad connection somewhere. You can always tell by looking at them either. You need to test with a meter.

 

[DaSouthWon]

I took the alternator to an alternator shop. He tested everything when it was dissasembled, as did I. He then checked it again after reassembly, under load. Everything checked out fine. All battery cable connections are fine, as are all the other various grounds and connections that I could find. This is why I can't figure it out.

 

[docvette]

Doc Here, imp:

As long as you have the Alternator OUT..Get a Diode Rectifier, and a Diode Regulator And install them, I think your problem will go away.

Just depending on the Alternator to Charge up a Battery is not going to get it on a Flat dead battery..At best it will replace lost surface charge..Charging systems were not designed to do that..they are designed to replace Surface Charge And support the system..more than that you can blow out the diodes.

Charge your battery at 10 amps for 12 hours. Repair the Alternator, and start it up..

Measure the voltage at the battery..It should read at idle, after warm up, 13.95 to 14.4 Volts..If it reads 12 volts or lower, It is not charging..and could be a fuse link on the alternator output wire. check and replace as needed..

If that is present, Configure your DVOM Meter For AMPS, Highest scale (usually about 10 amps) and remove the battery cable..Place one probe on the battery post the other on the cable..BE SURE all drain items are off..(domes, hood , interior lamps) and read the drain..It should be on a modern car, with computer and CD Player with active presets, between 0.3 and 0.8 (less than an amp) you will have to scale the meter down to its lowest setting without pegging to get the accurate reading. If it's higher, then you have something posing a load sitting..you need to trouble shoot that.

Doc imp:

 

[DaSouthWon]

I was planning on checking the draw by pulling fuses until the dvom dropped. I'll try this tomorrow. What I can't figure out is why the battery power was lower after driving it 60 miles than it was before I ever jumped it off. The radio was cutting itself off while I was driving. This is what lead me to think the alternator had no output. This specific car can be driven for about 3 hours on a fully charged battery with no alternator.

 

[docvette]

Doc here, imp:

Your main Fuse link May be open too BUT still touching..and your system is shutting down when you hit a bump..(It's in heatshrink) also would shut down the charging system If the link was tied there.. No Alternator link=No charge..Intermittant Fuse link= system shutting down and starting up under different circumstances..

Doc imp:

 

[pickler91]

i had a similar problem with my truck, i found that my stereo had been rewired and it was on a live wire, instead of being switched with the key, this could also be affected by interior lights, or even your wiper motors if they have gone bad, i know it may sound silly, but it will deffinately kill a good battery in a hurry.

 

[xntrik]

I agree with Doc.

Everyone should have a cheapo VOM handy and test the alternator voltage at the battery leads when the car is running for 14.0+. You can check voltage going down the highway by using the cigarette lighter socket to determine if it is intermittent.

Just did it this week.

Do the load test by pulling fuses one at a time to isolate the offending circuit.

 

[DaSouthWon]

Going out to get my hands dirty now. I really appreciate everyones help. I'll let you know what I find. I've got an industrial ac - dc transfomer that belonged to my grandfather before he died. If I remember correctly he used it to crank and run cars using it in place of a battery. This thing is huge, and heavy. 2' x 2' x 3' and probably weighs 100 pounds. Iv'e never seen another one. May help me with my troubleshootin'