charging problem r33 skyline

[squazy84]

an unusual problem ive had the last few days, the car i drive for summer has started to put on the battery light on the dash,so i suspected the alternator early on,but ive had it tested and its fine,
oddly the car only charges to 15 volts when the battery light is on, but when the light is off the voltage reads 11 or 12 volts when running,
Ive checked all fuses and most of the connectors i can see but im starting to run out of ideas
has anyone on here any experience in such a stuation?

 

[the snooper]

id say alternator, they connect straight to the battery, no fuses unless you nave a bad earth from / to the engine

 

[knighty]

15v is about right when it's working and light is off

11v or 12v with the light off means it's not working


sounds like alternator to me, but it's not a sure thing, could be a wiring problem


should be 2 wires coming from alternator, big heavy one is the main positive, it';; go straight to the battery (of maybe join to battery lead on back of starter motor etc..)

small wire is for the regulator, and this one does the battery light too - that wire is normally negative, and then turns positive when the alternator starts putting out power (so lights the bulb at first, then it should go off once alternator is producing power and bulb has positive to both sides of it)

 

[squazy84]

this is a mitsubishi alternator and has 3 wres

 

[MoreWellie]

Have you checked all the fuses?

lexus alternators also have another live feed which is separately fused to the light feed, I have a feeling that with this fuse blown it might behave similar to this. Not sure why the other feed is there though

 

[normspanners]

Some have a separate battery sensing wire so that it senses battery voltage and adjusts the charge more accurately if that wire is bad it can give allkinds of weird problems.

 

[squazy84]

yes i checked all the fuses, i was thinking of supplying the correct terminal with 12 volts to see if it helped,but i need to find a wiring diagram first

 

[The_Yellow_Ardvark]

15v is a wee bit to high, looks like the Alt. regulator is shot.
A simple test.
Ignition off. Measure battery voltage, across battery, with both meter wires on battery. Then with positive meter wire on battery and the neg. lead on any good engine earth. They should be aprox 12.7 Volts. May be 12.5 from across engine earth.


Ignition the volts should not change, it may drop 0.2 volt.

Fire up the car, again measure the volts at engine RPM about 800 to 900. The volts should be13.4 to 13.7 volts.

Switch every electrical device, volts will/ may drop but no below battery voltage. Bring engine revs up and the volts will raise to anything up to 14.2 volts.

If it goes over 14.2 volts or under load drops below battery static charge the alternator is on it's way out.

Battery light works on the potential difference between Alt charge and battery. Not fused, as it will add extra resistance in the circuit.

I am guessing you have tested the battery with a battery tester or had it "dropped Tested".
Again a good guess is you have checked the earth connections. Engine to body and battery to body connections.

Oh there used to be a an issue with the dash earth wire what would throw up "interesting" dash faults.

But I am guessing it is the alternator. They are cheep enough for new ones, not worth repairing the old unit.

 

[R33]

How old is the battery? Do you no if it is the one that came with the car on import? If the car is not used the battery will die and kill cells! Ive not long replaced my batt on my R33. That was a yusa battery from halfords , dint last no have a bosch much stronger battery. Has no problems starting if its left for a few werks or more!

 

[squazy84]

the battery isnt a bad one,it was replaced just last year,but it is from halfords

 

[The_Yellow_Ardvark]

Yusa battery are good battery. Just because cam from Halfords does not make it a bad battery.
The issue is the length of time Halfords store them.
A decent battery tester will show any faults.

 

[squazy84]

switched battery and its exactly the same

 

[R33]

the battery isnt a bad one,it was replaced just last year,but it is from halfords

Ok, i would test the battery see wot it is reading. If its low put it on charge if you can , to get it back to full charge! Then re fit and see how it goes.

I found that with doing it that way my car wouldn't start after leaving it for 2 days. And recharging it dint matter as a cell went bad!
But that was my car though, i dont drive mine much at all, so was bound to happen!

Try to eliminate the battery as the problem then lookat other possibilities. These are old cars now so parts are getting tired and worn out!

 

[R33]

Look at the alternator then if you have tried a different battery!