alternator problem

OK sorry for not being around much, been busy with work in this country and abroad not enough hours in the day

IM currently driving around in my mates MR2 whilst he is using my estate the car broke down 2 weeks ago with a dead alternator this was confirmed by testing the output on the alternator which was found to be sitting at 11v we did have warning lights on the dash which indicate the alternator was dead.

so the alternator went of to be repaired and had new internals regulators etc how ever 3 days later i noticed the battery level was sitting on 12v and didn't rise when i started the car so fearing the worst checked the alternator again and this time just under 12v so i know it had failed again.

I have returned it the company are saying that the car has caused the regulator to die possibly from over current but surely the only current the car can get is from the engine. any tips on whet to look for that could (possibly) indicate the car is at fault ?    

the car has had an engine change and is currently running a 3ltr toyota camry engine it has had this all the time i known the car and nothing changed on the car for it to allow the alternator to fail....

we also have the amplifier's installed in the car 1 of which is now in protect mode and has been since the alternator failed the 1st time so i reckon this is knackered now but could this have an impact on the car now ?

I was not on the phone with the company so I am not sure exactly what they told you. However, I will assume they told you as what you wrote, I think the company is BSing you. The regulator is what regulates the current putting out from the alternator. The over voltage could only occur from the alternator out ward to the accessories. If the voltage is lower than 13V with no accessories on when the engine is running, then the brushes might be worn out or the diodes are failing. The only way to check is to get a tester on it. Some good tester will tell you whether the diodes are failing or not.
Now if you have high power amps, they will effect more on other accessories like the head lights, or any other high current draw devices. What I would do is turn off all accessories and put a voltmeter on it while the car is running to see what voltage is. It should be 14V to 15.5V range. Then turn on the amps and see what voltage is when they are on. If the voltage drops then you need to upgrade the alternator.
What is the brand of your alternator?
I hope this info helps.
Good luck and keep us posted.

If it were a Bosch alternator, I'd say you had a dead battery.
But Toyota probably uses ND.

Have the battery recharged externally - it may have collapsed.
Ensure it holds 12.6-12.7V when fully charged and recovers to about the same voltage with headlights on for 5-15 minutes.
Note that after a 13.8-14.4V recharge, it should hold a "surface charge" and hence a voltage up to ~13.6V.


A faulty battery or heavy load could be pulling the alternator output voltage down.


Worn brushes can limit the alternator output.


The regulator should not be effected by over-current - ie, load exceeding alternator output.
Regulators actually regulate the alternator's output voltage (by regulating rotor current) - not the current, but the output current-voltage relationship is determined by the load (V=IR) and alternator speed & condition.


Good alternators should not be damaged by overload, but many are rewound OEMs (and the rest are Bosch LOL).

You could try to load test the battery. Even a battery showing 12v does not mean it's good under cranking. Some thing really important I forgot to mention, check the connections to the alternator and battery.

ok sorry for the delay in the update

we have had the alternator repaired again and is holding strong however i did do a few changes to the car to ensure we were getting good distribution
new feed from Battery to alternator
New feed from battery to chassis
New feed from chassis to engine

We will be fitting new feed from fuse box to alternator, but i have been out the country again yawn starting to wonder where i should be living lol

So far so good no more issues the voltage seems stable and the car starts on the button, i suspect as well that the refurbishment of the alternator may not have been done to the high standards i expect....

but cant fault them in the fact they did get on and do it.....