7 replies to this topic

[felixy69]

My battery light is constantly on
But battery has at least 12v when car is off and when car is on, the alternator is charging at 13.4v

Why is my battery light on ??

[Italianjob]

Have you had any starting problems? Does the battery sound healthy when you try to start it?

Have you tested the battery under load? Some times putting a volt meter on it is not enough to determine if it's duff(faulty cells can hide themselves well)

All terminals on the battery are good and clean with good contact?

Could be something even more simple like a bad earth.

Have you installed anything new that could draw too much of a current?

[tiger99]

It is not a battery light, it is an alternator light. It tells you ONLY that the alternator is not charging. And 13.4V is too low, you need to see 14.4V.

 

Most likely your alternator is faulty, or the alternator side of the lamp has shorted to earth, which may prevent the alternator working properly. The current through the lamp is necessary for initial magnetisation of the armature coil. So pull out the alternator plug (NEVER run teh engine with it out) and check that the lamp is now out, with ignition on of course. If it stays on, you have a wiring fault.

 

Before condemning the alternator, thoroughly check and clean the engine and battery earths, battery positive terminal, and the stack of wires on the solenoid battery terminal. That means taking them apart, cleaning the faces with a mild abrasive, and tightening them up carefully. Check the fan belt and pulleys. Get all the cheap fixes done first, before trying the expensive one, a new alternator.

 

But before you do any of that, maybe you could tell us whether you have done anything recently to the car, and when did the problem arise, just in case there is something else that we can suggest.

[Italianjob]

Disregard my post and listen to this guy ☝️

[tiger99]

Italianjob, what you said was good, and definitely worth checking too.

[felixy69]

It is not a battery light, it is an alternator light. It tells you ONLY that the alternator is not charging. And 13.4V is too low, you need to see 14.4V.

 

Most likely your alternator is faulty, or the alternator side of the lamp has shorted to earth, which may prevent the alternator working properly. The current through the lamp is necessary for initial magnetisation of the armature coil. So pull out the alternator plug (NEVER run teh engine with it out) and check that the lamp is now out, with ignition on of course. If it stays on, you have a wiring fault.

 

Before condemning the alternator, thoroughly check and clean the engine and battery earths, battery positive terminal, and the stack of wires on the solenoid battery terminal. That means taking them apart, cleaning the faces with a mild abrasive, and tightening them up carefully. Check the fan belt and pulleys. Get all the cheap fixes done first, before trying the expensive one, a new alternator.

 

But before you do any of that, maybe you could tell us whether you have done anything recently to the car, and when did the problem arise, just in case there is something else that we can suggest.

 

 

 

before this happened, i had radiator, water pump, thermalstat, and heater hoses replaced ....after all this, the lamp wwent on

[gazza82]

Is the fan belt slipping?

[tiger99]

It does seem that it is so, or (much less likely) the alternator wiring was somehow disturbed in the process, causing a short. But in the circumstances the fan belt has to be the first thing to check, and as it is a low vakue consumable, the slightest doubt about its condition should call for replacement.