Hi all I just rebuilt my alternator ( I assume it rebuilt back to oem 120amp) due to it failed few months back . When I started the car today the batt warning sign came on , i off and restart after 5 mins the warning sign came on . I tested using cigarette lighter voltmeter and it shows 10v and around 10.8 when I start the car so this shows clearly issues with alternator . So I decided not to drive the car today and went for lunch . I read about loose alternator wiring on my way back . After I came back I open both front and back bonnet ready to check the loose wiring , what strange is the batt warning sign is gone ( I didn't touch anything except open the bonnet ) and the volt meter read about 13.6v when I start the engine . But the 13.6 could drop to 13v . So I decided to take for a drive and I have a few questions to ask Here is how the voltage read 1) running with stereo , lights on and A/C on - 12v to 12.5 v sometimes 12.8v unless I accelerate fast will go up to 13 v ( to me this is still low) 2) when I stop at red light with stereo on, light on and A/C on it only shows around 11.5-11.8v My question is - I am wondering if my alternator has enough AMP. I suspect something is lacking in my alternator. Maybe the quality of rebuilt is bad ? The voltage reading is very low . I know that our oem alternator has 120amp but with today need and technology , amplifier, stereo , AC and light on I am not sure if 120 amp is enough ? Has anyone install a larger ampere alternator ? If yes what brand and product ID? Or rebuilt to a larger ampere alternator ? Thanks Sent from my iPhone using Tapatalk
Leslie, something is going on obviously, you should never fall below 13.8V. But one very important thing, measure the voltage using a proper voltmeter, not using one of these cigarette lighter thingy. I also bought one to monitor my voltage as I was driving, but quickly realized that I had a 0.8V difference between the actual voltage at the battery and ts the cigarette lighter voltmeter. I measured the voltage with a proper device at the lighter and was getting again 0. 8V more, so these cheap voltmeter are quite inaccurate. Do the same measurement I did, because if you have something like 13.6v+0.8v=14.4v, then you know you get the right voltage in some conditions. Verify the alternator is outputting more than 14v, at least, and consistently regardless of what you turn on in the car. If you can achieve this in some conditions, then the alternator is good and you can start tracking the excitor wire (yellow). Otherwise, your regulator might be faulty. Did you wiggle the alternator plug with the engine running to see if the voltage was changing? Be very careful if you do this, the alternator fan blades are two inches away... Verify also the plug under the tank, but you've probably read my recent thread.
I often tested the voltage of my generator because it seems always strange to me when the voltage goes down to 13,1 V with about 2500 rpm. but when the 2 fuel pumps running, the radiator fans and the ac and also the lights are on then it is normal at my car. when I go to 3500 rpm the voltage increase to 13.4V. I meassured with a digital voltmeter as soon as the radiator fans are off I have again 13.5 V and when the AC is off and the lights are off I have mostly 13.9 to 14.2 V, so in my eyes all ok but if you have a charging voltage below 13 V at 2500 rpm you may check the generator. the regulator is inside the generator. but you may meaasure also the voltage ourput at the generator, not what is coming at the battery. also I tested once the amp what the generator brings: with totally empty battery and all fans on, AC on and the lights also I meassured 95 amp. you may test this also, best woukld be to use a battery you know it is totally empty and may be also dead. so jumpstart the car and take the good battery away.
Thank you for all the info , I will make sure I get the proper voltmeter and test again . Something very strange is ( assuming there is +_ errors in my cheap cigarette voltage reader) when I check on the voltage when I start the engine and with just AC on it shows 13.4 which is good , the moment I push the accelerator the voltage drop to 12.1 as per the video attached below . It seems to me the alternator is not consistently charging which is strange . Especially when accelerate we should get more voltage https://vimeo.com/164988335 Sent from my iPhone using Tapatalk
this seems to me as if the belt has not the right ension? because when you accelerate it needs more electricity. but check on the alternator itself, only there you get right meassurments
Yes, joe is right, measure the voltage at the alternator, and see if you get the same. Check the 9-pin plug under the coolant tank.
Yes you guys are right , when I measured the alternator reading it gives only 11V and the battery is down to 200A instead of 650A full. The alternator is not working and the previous rebuild has issues. I have sent the alternator to the shop that rebuilt the alternator and this time I will ask them to upgrade the alternator to 130-150A instead of 90A so that I could charge the batt more due to I seldom drive my car. Sent from my iPhone using Tapatalk
Keep your battery fully charged with a tender all the time if you rarely use the car. The worst enemy of the battery is not be fully charged. Then the alternator has to work harder every time you start it for a much longer time than with a charged battery. Keep in mind an alternator is NOT a battery charger.
