Alternator Charge light issue. Prolem solved

[unlimitedpower]

Well today was the day my primera was meant to be picked up by its new owner and i took it for a bit of a drive as it hadn't been run in a few weeks.

After about 5-8km of driveing and the car was warm the charge light came on.
Now this really really pissed me off.

It did that a couple of weeks ago and i found that the bolt for the alternator belt had come loose. I tightened it up and it seemed to be all good. (the car had cooled down for a few hours).

I suspect that this problem is only when the car is warm.

I have put a multimeter across the battery and im getting 14.95volts while the car is running.
14.65volts with the lights on.

I compared this with my bluebirds and Mazda Demio and this is what i got.
Car running lights off.

Primera = 14.95volts (the problem car)
Bluebird 1 = 14.02volts
Bluebird 2 = 14.53volts
Mazda Demio = 14.43volts


Is this voltage reading to high? I suspect that the alternator is going to need replacing.
What are your thoughts i need help asap on this one as the girl who brought the car needs it asap and i don't need the stress.

Any help would be great.
Thanks

[mint16]

overcharging definitely.

[fast4motion]

It's possible that the alternator is "sensing" a lower than true voltage (dodgy wiring which heats up and increases in resistance, or a poor connection, therefore lowering the voltage at the alternator which it uses to self-regulate). Which means the alternator is increasing it's output to what it thinks is the correct voltage.
To test, you could try installing a jumper wire directly from the alternator output to the "S" terminal. This means it'll sense it's actual output voltage and hopefully regulate to a lower voltage. If not, then it'll probably be the alternator on it's way out.

On an old-school car, overcharging wouldn't illuminate the charge light, as both sides of the light would still have the same voltage. I'm not sure about modern cars, but I wouldn't have thought a difference of 1 or 2 volts from the alternator would be enough for the light to come on.

[unlimitedpower]

Hmm most of what you said makes sense i think the alternator is on its way out.
Little confused by what you said about the jumper wire to the "S" terminal i'll try start it up in the morning see how it goes then.
Suppose i should be looking for a cheap replacement.

[fast4motion]

Yeah, it's a little hard to explain in writing. Was just a cheap/free way of eliminating the car wiring as being the problem.
Chances are it'll be the alternator though.

[unlimitedpower]

Started car this morning and it charged at 15.34volts.
So im going to buy a new alternator and fit that.

Let me know if anyone wants to buy a alternator that works even better than a normal one.

[unlimitedpower]

Well solved the problem after buying a new 2nd hand alternator putting that on same situation.
So i went and got another alternator (which i forgot i kinda owned as i have half paid off an engine i have to pick up some time) would have saved me buying the other one.

Still no change. Now i was starting to get pissed off.

Turns out it was the large wire on the two wire plug. When the plug was pushed in instead of the spade terminal slipping over the male part as it should it was pushing the wire out of the plug i only fixed it by shoving my multimeter in there to see what the voltage was when i did that i noticed the wire slip down about 4mm and bingo all fixed.
10hours of messing around later and it was just a stupid loose wire. Pain in the arse thing was i would have unplugged and replugged in that plug at least 10 times.

Well at least its fixed sold and money in the pocket now.

Anyone want to buy a SR20 Alternator cheap good working order i have two spare ones i don't need now.