Alternator charge warning light comes on & off periodically

Can any body shed some light on this problem. Lately the alternator warning light has been coming on and off usually happens when I first start heading out for drive after starting but can come on and off at any time and any rpm, volt meter shows no charge when the light comes on so the gauge seems to be correct tried changing the bulb no change. Had the alternator checked it and even swaped it problem was still there. Checked everywhere for loose earth or bad connection can't find anything. Battery is run through an isolator via 100 amp fusible link to the starter and alternator, all circuits are using relays and are fused. I can't isolate the problem I thought it may be related to the immobiliser however if is was caused by the immobiliser every should stop working but the car keeps running of the battery.

Any on got any ideas.

Mick
 
I think hes not driving fast enough. Get some rpms on that alternator when you start up.
You possibly might have a big ground fault that is like a wire rubbing up against a piece of metal intermittently. It isn't a fused wire, so it may be your big wires from the battery. Or at the battery. What ever it is your shunt is more than your alternator can put out. Sounds like you need to do some continuity testing throughout the car!! Clean off all the connections at the battery, alternator and starter. Make sure that there are no loose internal connections in those areas. This sounds like your charge from the alternator is going nowhere. Like when the belt is slipping. Is the belt too wide for the V grove in the alternator(assuming you have V belts here). These are the only ideas I have(for now).

Bill
 
I think hes not driving fast enough. Get some rpms on that alternator when you start up.
You possibly might have a big ground fault that is like a wire rubbing up against a piece of metal intermittently. It isn't a fused wire, so it may be your big wires from the battery. Or at the battery. What ever it is your shunt is more than your alternator can put out. Sounds like you need to do some continuity testing throughout the car!! Clean off all the connections at the battery, alternator and starter. Make sure that there are no loose internal connections in those areas. This sounds like your charge from the alternator is going nowhere. Like when the belt is slipping. Is the belt too wide for the V grove in the alternator(assuming you have V belts here). These are the only ideas I have(for now). Have you done any work on the electrics lately? to the volt meter? anything with a big wire or draw of current?

Bill
 
Jim thought about leaving it in the driveway but can't stop want to drive it, how ever if the an internal reg has gone the second alternator I tested shouldn't do the same thing.

Bill always drive fast as I can I mean as appropriate :) if there was a short I would expect to see smoke it sound like a doggy connection just can find it and it's pissing me off.

Mick
 
Sorry Mick missed the bit about swapping it (new or known good one).
Yes connections or something of that nature.
I am assuming int reg not external.

When it happens, what does the volt meter read at the battery and also at the output on the back of the alternator.
It may give you a clue


Jim
 
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Ian Anderson

Lifetime Supporter
How old is your battery and is it a lead acid one.
If so I would bet it has a buckling plate in one of the cells and occasionally it manages to short out.

If you are running a gel betters it blows my guess out the water

Ian
 
Jim Int reg on mine, tried another Alternator still did the same thing, volt meter shows voltage at the battery when the light comes on approx 12 volts, as soon as the light goes off charge comes on up to 14 volts. There are only 2 wires on mine so its either a short to from the bulb wire or a bad earth I think, I dont have any f#*ken idea.

Ian the battery is a dry cell 900amp unit.

Frustrating
 

Pat

Supporter
Assuming your battery is good, connections are sound, and alternator properly functioning, so not to be captain obvious here but are your belts tight and in good condition? They may be slipping when the alternator is pulling a lot of torque to replenish the battery at startup. Also, do you know if you have an underdrive pulley? Some builders use them to reduce alternator drag at the expense of lower alternator RPM - and charge. This is especially evident at low RPM and driving speeds. A combination of an underdrive pully and glazed or loose belt could cause what you describe.
 
Hi Mick
Have you checked the volatage at the sense "S" terminal on the int reg connector, should read the same as the battery.
Try connecting a bridge wire from the main alt power lead on back of alt to the "S" terminal on the reg and take it for a run.
If that doesn't work, take another bridge wire with a 2W bulb inline and connect one end to the main alt power lead and the other end to the "L" terminal on the reg (completely bypasses the cars electrics, make your you dont leave it connected afterwards)
If its still playing up, look at your fusible link and wire back to the battery from the alt.
hope that helps

Clayton
 
Hi Mick
Have you checked the volatage at the sense "S" terminal on the int reg connector, should read the same as the battery.
Try connecting a bridge wire from the main alt power lead on back of alt to the "S" terminal on the reg and take it for a run.
If that doesn't work, take another bridge wire with a 2W bulb inline and connect one end to the main alt power lead and the other end to the "L" terminal on the reg (completely bypasses the cars electrics, make your you dont leave it connected afterwards)
If its still playing up, look at your fusible link and wire back to the battery from the alt.
hope that helps

Clayton
Thanks Clayton I think it's a connection problem / earth intermittent break in contact caused by vibration. Going to rewire main fuse panel install mil spec connectors to make it easy.
 
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