Battery light on, off when start the car?????
Discussion
Battery light was on so I changed the battery as it was 7+ years old anyway. Thought this would solve the problem but the battery light is still on!!!!!!!!!!!!!!. Took EVERY fuse and relay out and the light stayed on. Checked the big fuses and all seems fine. Took the charger off overnight and the battery was 12.9v when I took the charger off and this morning it read 12.4v. Started the car and the light goes out and the battery reading is 13.9v. Any ideas as I'm at a loss?
FFG
FFG
FlipFlopGriff said:
Battery light was on so I changed the battery as it was 7+ years old anyway. Thought this would solve the problem but the battery light is still on!!!!!!!!!!!!!!. Took EVERY fuse and relay out and the light stayed on. Checked the big fuses and all seems fine. Took the charger off overnight and the battery was 12.9v when I took the charger off and this morning it read 12.4v. Started the car and the light goes out and the battery reading is 13.9v. Any ideas as I'm at a loss?
FFG
If you understand how the light illuminates, it might help.FFG
Usually, in a simple system (not ecu controlled), the light illuminates when ignition on, engine off. This is because the light has two feeds - one from the battery, one from the alternator.
The voltage differential across the bulb is high enough that it illuminates, as a warning that your alternator is not charging. Your engine is off, at this point.
When your engine is running and your alternator is charging, the voltage from the charging alternator is felt on the other side of bulb. Now, the differential across the bulb is not enough to illuminate it. This tells you that the battery and alternator are either OK, or both supplying the same voltage.
In your situation, that battery is OK, and your alternator is producing 13.9 (FYI, anywhere from 13.5 to 14.4 volts can be considered normal). It tells me that you should check your wiring - if a feed from the alternator is damaged, it could cause your illumination. I say this, as when your ignition is on, engine off, the light illuminates.
TobyLerone said:
If you understand how the light illuminates, it might help.
Usually, in a simple system (not ecu controlled), the light illuminates when ignition on, engine off. This is because the light has two feeds - one from the battery, one from the alternator.
The voltage differential across the bulb is high enough that it illuminates, as a warning that your alternator is not charging. Your engine is off, at this point.
When your engine is running and your alternator is charging, the voltage from the charging alternator is felt on the other side of bulb. Now, the differential across the bulb is not enough to illuminate it. This tells you that the battery and alternator are either OK, or both supplying the same voltage.
In your situation, that battery is OK, and your alternator is producing 13.9 (FYI, anywhere from 13.5 to 14.4 volts can be considered normal). It tells me that you should check your wiring - if a feed from the alternator is damaged, it could cause your illumination. I say this, as when your ignition is on, engine off, the light illuminates.
Engine is off, key isn't even in the ignition and the light is on.Usually, in a simple system (not ecu controlled), the light illuminates when ignition on, engine off. This is because the light has two feeds - one from the battery, one from the alternator.
The voltage differential across the bulb is high enough that it illuminates, as a warning that your alternator is not charging. Your engine is off, at this point.
When your engine is running and your alternator is charging, the voltage from the charging alternator is felt on the other side of bulb. Now, the differential across the bulb is not enough to illuminate it. This tells you that the battery and alternator are either OK, or both supplying the same voltage.
In your situation, that battery is OK, and your alternator is producing 13.9 (FYI, anywhere from 13.5 to 14.4 volts can be considered normal). It tells me that you should check your wiring - if a feed from the alternator is damaged, it could cause your illumination. I say this, as when your ignition is on, engine off, the light illuminates.
FFG
Ignition on, engine off current flow is from ignition switch, through lamp and to ground inside the regulator.
Engine running and the alternator starts charging current is applied through the regulator to the ground side of the lamp. Voltage either side and the lamp goes off.
Your problem is that the regulator has failed, probably a main + diode, and current is being applied through the regulator to the lamp, and to ground via other circuits connected to the ignition switched supply.
Engine off, ignition off and disconnect small wire to alternator, you should have 0 volts on th alternator terminal.
This fault has nothing to do with the regulator
What is happening is the Alternator has faulty diodes that are allowing a 12 Volts Positive through to the Alternator ignition warning light terminal
You mention that when you start the engine the light goes out, I suspect that when you turn the ignition on before starting the engine the light goes out. There is a big difference between these 2 scenarios
What is happening is the Alternator has faulty diodes that are allowing a 12 Volts Positive through to the Alternator ignition warning light terminal
You mention that when you start the engine the light goes out, I suspect that when you turn the ignition on before starting the engine the light goes out. There is a big difference between these 2 scenarios
phillpot said:
May be a generalization and not wishing to insult anybody but if you need to ask "how to fix" possibly stripping and rebuilding an alternator is not for you?
New or exchange unit, out the box, bolt it on and everything sorted plus a warranty
New or exchange unit, out the box, bolt it on and everything sorted plus a warranty
Regulator/rectifier what does it matter? A diode has gone, the alternator's stuffed.
No one in their right mind is going to strip an alternator even if you could get parts to rebuild easily.
Whatever way the only way forward, as Philpot said, exchange unit, everything new and warrantied.
Mr Jenks said:
Regulator/rectifier what does it matter? A diode has gone, the alternator's stuffed.
No one in their right mind is going to strip an alternator even if you could get parts to rebuild easily.
Whatever way the only way forward, as Philpot said, exchange unit, everything new and warrantied.
Tried to check the connections on the alternator so tried to get it off as access is impossible but couldn't get it off but jiggled it about back and forth, so put the bolts back in. Guess what, the light has gone off!! Maybe a dodgy connection so I'll take the coil off to see if I can get access to the studs on the back.
FFG
FFG
I obviously disconnected the battery before I started messing with the alternator and when I connected it back up I got the 3 blips from the alarm system which it hadn't done prior to that - not sure if that's coincidence or related.
Will have a jiggle of the spaghetti in the footwell to see if it comes back on.
FFG
Will have a jiggle of the spaghetti in the footwell to see if it comes back on.
FFG
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