Ive just put a Fiesta back on the road after three months sitting on a neighbour's driveway.
She started fine, the charging light going out after about 5 seconds.
It has had a new alternator fitted by the previous owner as he said the battery wasn't holding a charge.
Today the battery went completely flat while my daughter was driving it.
The RAC man said the battery was showing 7.1v and, in his opinion the charge light wasn't working at all.
I was wondering if these cars have some sort of regulator like the older Fords I use to play with in my youth. These things would go wrong for a pastime.
As the alternator is recent I don't suspect it (although I don't rule it out).
Any ideas where to start looking?
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the alternator
its a big thing to the left of the engine
when you have found it check the main power cable that goes from it to the battery or indeed it might go via the starter thats the big thing on the right and then to the battery
why didnt RAC man check charging system with engine running though?
regulator is built into the back of the alternator
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Hi Bell Boy, found the alternator ok, you were right it is the big thing on the left, it's also a very shiny thing.
I've checked all the connections they're all tight.
Quite why RAC didn't check the charging system I don't know, perhaps he was in a hurry, perhaps dealing with a young girl ... wouldn't understand etc, who knows, pretty poor whatever the reason.
How can I check the charging system? I have a meter.
Also he's right, the battery light isn't coming on at all now, could this be a clue? (It may not have been coming on all along mind you, I probably confused it with the oil pressure light).
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As a starting point you should be seeing 13.5 - 14 V across the battery when the engine is running above idle.
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Doesn't look good, it's only 11.9 volts across the battery, revving the engine makes no difference ... still no battery light with just the ignition on either?
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I've just checked the bulb behind the dash and that's working ok if I change it with its neighbour so there is no power going to that with the ignition on and the engine off!
All very strange, any thoughts?
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If I understand you correctly and the ignition light doesn't come on when you switch the ignition on, that's an indicator of the problem. The small ammount of current supplied to the alternator rotor through the bulb is what initiates the charging process, if as you say the bulb is OK, either the other end of the lead is not making contact with the small connection on the alternator, or the new one is faulty.
You could check by connecting the small and large terminals together briefly with the engine running, if the alternator is OK this should start it charging until you turn the engine off again.
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Hunting around the forum I can only find one reference to the dash light not coming on and then it wasn't really answered.
Could it be an earthing problem? I'll go over all the connections in the morning ... cleaning and tightening all of them as I go, fingers crossed it solves the problem!
Any other ideas/tests I can try?
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Concur with Peter N on this.Another test that can be made is to remove the connections to the alternator and check for battery live voltage at the large fat (red )lead.Also with ignition on,(engine off),earth the blue wire.This should illuminate the batt warning light on the dash.If this all checks out ok,then alternator is suspect.hth
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Thanks Peter N and Elekie, I'll work on it at first light tomorrow and let you know the outcome.
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Peter N:
I put the battery on charge for a couple of hours, it now reads 12v.
I've removed the cover on the alternator and checked the connector on the back of the alternator and it seems to be making a good contact.
With the engine running I've connected the small and large terminals together, both directly and then replaced the connector and also with the connector on and then connecting the other ends, the battery still shows a steady 12v, I presume it should show a higher voltage as the alternator should now be charging.
Elekie@a/c doctor:
Removing the connector on the alternator I successfully read a live voltage on the large red lead. This shows the wiring to the battery is ok.
With ignition on (engine off) I earthed the blue wire. This had no effect and did not illuminate the batt warning light on the dash ... would this suggest the alternator is ok (it is a replacement after all) and that there is another fault?
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The batt/charge warning light needs to work for the charging circuit to operate correctly.Follow the wiring loom from the alternator where it hooks up to the starter motor.There should be another connection for the blue wire.hth
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Yes, I found the connector, this is where I have been connecting to the blue cable.
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OK,so disconnect the connector and earth the wire from the car side ,not the cable running to the alternator.If still no warning light ,then there is a break from this point to the dash pod.hth
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I've been following this thread. I agree with everything that Peter N. and elekie&a.c doctor have said.
Reminds me of a car I had this problem with some years ago. Got stranded because the battery went completely flat while I was out, had to call the AA out to take me home.
After pulling out all the dashboard to change the Ignition warning light, which turned out to be fine, the actual fault was eventually traced to the wire which came out of the alternator and went up to the warning light. This curved rather sharply as it left the alternator, with a result that the copper cable had fractured inside the PVC insulation. The result of this was, when visually inspected, the cable looked OK, but when tested with a meter there was no continuity. Problem solved!
I hope you manage to find the fault on your car, OP, and, from my example quoted above, don't take anything for granted. Test everything thoroughly, and good luck!
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Hi elekie&a/c doctor, Just got in from work and immediately tried what you suggested, can't believe I was trying the wrong side of the plug ... doh, anyway trying the right side and the battery light illuminates, progress at last.
Does this mean that the alternator is up the creek?
Edited by cliff on 24/07/2009 at 21:19
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Yes,looking very likely to be alternator u/s.hth
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Replacement alternator fixed all problems, less than £50 too.
Thanks to all who helped, I've learned a lot about alternators and charging circuits and maybe others will in the future.
Thanks again.
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a bit late in response but , the diodes pack up and drain the battery back through the windings
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It makes sense-particularly if doing a lot of short journeys-not to do a straight exchange but to fit an alternator with a higher output.
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