Ok, the story: In December my alternator stopped charging the battery so I went and looked at my options, rebuild at a shop, or buy a rebuild at a local parts store? I opted for a rebuild at a shop. Took it to the shop and got charged 160.00 CAN for a rebuild. The guys said the diodes were toast. So I also purchased a new battery cause mine was 4 years old and I thought its just good insurance to get everything tip top. 1 month later I noticed a high piched wining noise from under the hood. I didn't know what it was and then the car started to run rough. Got it home and the alternator was putting out around 19 to 21 Volts at idle, holly ****! I also noticed my air pump was not spinning the magnetic clutch. So I took it back to the guy and he replaced the voltage regulator(which I thought would have already been done with the first rebuild - he couldn't really answere that so I took it as a no. I also had to replace the air pump). Put it back in then 3 months later the diodes went again, took it back and he replaced the diodes with "better" ones, yeah right! This time he wanted cost on the parts witch was another 60 bucks after taxes. Ok, well last week it started overcharging again. around 20 Volts at idle. I have been patient with the guy, been nice and understanding never asking for anything more than to have the job done right. I'm at the point now where I want to say screw it and I'll just go buy an alternator at the local parts store. Before I do that I was wondering if anyone has any ideas what would be going on?? Could there be something wrong with the winding or the stator? I have tested everything, checked all points, grounds, everything. Another thing to note - I will not drive it when its putting out all those volts. AND its running rough again at idle. But, at least my replacement air pump is still working. Could this problem have damaged anything else on the car to make it run rough? Again, any help would rock guys. later, Kent.

 

Anyone have any ideas? please I know its quite the read but, I hope my info helps.

 

A close friend of mine went through the same thing with his alternator. After acouple tries with his (the shops) replacement parts the guy got OEM Mazda replacement parts for the alternator and hasn't had any further issues with it.

 

has he checked the alternator on a bench test. It may have a bad winding. Does it work for a while and then crap out or is it bad from day one when you get the car back??

 

Ya, the guy has all the equipment, I saw him bench test it. He just opens it back up and replaces what is toast and gives it back. I'm thinking he'd do a better once over and check all possibilities. I'm thinking it may have something like a bad winding too but, I don't know what I bad winding would do...........would it up the resistance causing things to burn out? Ya, it works great for like a month or two then it craps out again. I'm more worried at this point whether running at 20 volts idle would have hurt anything else in the car. Right now it runs rough. I will go back one more time to the guy asking is he would help in buying one from a store, I don't want him to try and rebuild it anymore. Also, since I have a new battery, now being 2 times its overcharging on it, would this kill my new battery?

 

I would not run the car at 20v float. You could damage the engine electronics and as you say fry the battery. Normally it floats at 15.2v or so.

 

I will not run it like this. I did start it last night and now its not charging at all. Other than that, the time it was overcharging and I did not know about it, what would be damaged in the engine electronics?