Discussion
Hi as the title says i am having problems with the car charging sometimes but not all the time. I have put a new battery on to eliminate that taken the alternator off to be tested and the chap that is doing this can't find a problem yet the one thing that he said is strange is we have 3 wires going to the back of the alternator the main one, the middle one which puts the light off on the dash and another one with a spade connector. He said if there is a problem with whatever this wire goes to it could cause a charging problem. I have checked the 100 amp fuse and the one earth from the block to the chassis and all look fine but haven't had a chance to check the earth from the battery.
Any help and feedback would be great thanks.
Any help and feedback would be great thanks.
You say it is not charging but don't say what the charge lamp is doing.
How did you check the 100 amp fuse? You must undo at least one of the cables from the fuse holder. If the fuse blew it would be black and melted but this is not the normal failure mode. The norm is a fracture due to vibration which can be 1. very difficult to spot and 2. can give intermittent charging.
Steve
How did you check the 100 amp fuse? You must undo at least one of the cables from the fuse holder. If the fuse blew it would be black and melted but this is not the normal failure mode. The norm is a fracture due to vibration which can be 1. very difficult to spot and 2. can give intermittent charging.
Steve
The middle ring terminal should have 12 volts on it with ignition on, it comes via the warning light.
It could be possible the warning light has blown, very unusual but not uncommon.
The fuse (16) is the same as the oil warning light so if this is working then that should be ok.
I’d be checking voltage at both sides of the warning light first.
Has to be a dodgy connection somewhere I would have thought.
It could be possible the warning light has blown, very unusual but not uncommon.
The fuse (16) is the same as the oil warning light so if this is working then that should be ok.
I’d be checking voltage at both sides of the warning light first.
Has to be a dodgy connection somewhere I would have thought.
As said fuse16 supplies most things on the dash so must be good.
Go to alternator and disconnect the Brown/yellow wire. With the ignition on touch that wire against a good earth on the engine.
If the charge light is on then a fault is present in the alternator (or the wire was connected in the wrong place on the alternator). If not then it is time to take the dash top off and dive in.
Steve
Go to alternator and disconnect the Brown/yellow wire. With the ignition on touch that wire against a good earth on the engine.
If the charge light is on then a fault is present in the alternator (or the wire was connected in the wrong place on the alternator). If not then it is time to take the dash top off and dive in.
Steve
Sorry to repeat earlier comments, but to my mind there are three possible causes:
1. A cracked 100 amp fuse (under the car, alongside the sump).
2. A failing alternator
3. A poor earth, including a poor battery connection.
Are you sure you have checked the 100 amp fuse under the car, and actually completely unbolted it? You are unlikely to spot a hairline crack, but the unbolted fuse will come out in two pieces.
1. A cracked 100 amp fuse (under the car, alongside the sump).
2. A failing alternator
3. A poor earth, including a poor battery connection.
Are you sure you have checked the 100 amp fuse under the car, and actually completely unbolted it? You are unlikely to spot a hairline crack, but the unbolted fuse will come out in two pieces.
So a recap then.
• If the lamp comes on at ignition then the lamp is working and the alternator is earthed.
• If the lamp goes out at start up then at that point in time the alternator is giving a charge signal.
• If the lamp comes back on again (solid) then we are back to point one but most likely the alternator has an intermittent fault.
• On other points the only way the 100amp fuse could come into the equation is if the lamp was dim indicating there was a difference in voltage between the battery and alternator.
• The lamp would not be working at all if there was a bad earth and the OP would be reporting many other systems playing up.
Steve
• If the lamp comes on at ignition then the lamp is working and the alternator is earthed.
• If the lamp goes out at start up then at that point in time the alternator is giving a charge signal.
• If the lamp comes back on again (solid) then we are back to point one but most likely the alternator has an intermittent fault.
• On other points the only way the 100amp fuse could come into the equation is if the lamp was dim indicating there was a difference in voltage between the battery and alternator.
• The lamp would not be working at all if there was a bad earth and the OP would be reporting many other systems playing up.
Steve
Penelope Stopit said:
storm grey said:
the light dosent come on the dash this is one of the strange things and yes i have taken the fuse all the way out to have a look at it .
By this, do you mean that the battery warning light (ignition Warning light) doesn't illuminate when you switch the ignition on?storm grey said:
ye when ignition is on the lights for oil and charging are on and as soon as the car starts they all go off. but when the car isnt charging the light dosent come on as it shoul to indicate that its not charging but as i said sometimes its charging and other times its not .
I don't know where you got the information from about how the warning light works as you are getting it all wrongThe light will often not come on when the alternator goes off charge, it will glow if there are any faulty diodes in the alternator or when certain wiring faults occur
During running the engine and the light having gone out as it should, the light won't come on as a warning if any of the following alternator components fail
Brushes
Regulator
Rotor
Any of the above can have intermittent faults, the brushes can be worn out yet still make contact with the rotors slip-ring when cold and then not do so when the alternator warms up
The regulator can go open circuit when warm
The rotor windings can go open circuit at any time
How do you know it's going off charge?
it all started when i took it for a mot and the car started missing stopped to investigate and then the car wouldnt re start as battery was dead .got a battery in the foot well and connectedjump leads and away to go .when i got home i put a new battery on the car and seemed to be ok i thought problem was solved. a few days later whent out for a run first time i stopped i put my meter on the battery and it was charging fine but when i got home i went to put my windows up and thought they were slow so put my meter on and saw that it wasent charging but a few seconds later the engine tone changed and it started charging again.so all in all very intermittant.
Many years ago (2008) I had a similar experience but was a long way from home when the car cut out with a flat battery. RAC diagnosed duff battery and changed it but the same thing happened a few days later. After investigation I found dirty contacts on the alternator, no problems since and the same battery 10 years later. Battery was expensive but cannot complain at 10 years use and still fine.
storm grey said:
yes have completly removed the fuse. alternator is being checked at the moment he has run it up on his jig for half a hour with no probs have checked earth from engine to chassis but not looked at the earth from battery yet not sure how easy it is to get at.
What was the outcome of this test?Did the person testing it remove the brush-box for a visual check?
the chap who i bought the altinator off who is very good has run it up on his jig again today but cant find a fault the only thing that consernes him is the terminal on the rear marked (w) does any body no were this goes to on the car please he said if there is a problem with what ever it goes to it will cause the altinator not to charge .thanks.
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