Intermittent battery light

[wilcoxc]

I've had a new battery and alternator fitted and occasionally after starting the car the battery light comes back on and stays on, unless i rev the car to around 3000 rpm then it goes off and stays off. This doesn't happen every time i start the car however. I've tried locating the 3 wire plug on the alternator but can only find a single blue/black wire(i'll attach a similar picture to what it looks like.) The alternator seems to go into a default charge when the light is on, putting out 13.7 volts, when there is no light on it puts out 14.6/8. i read a thread here https://www.fordmpv.com/smf2/technical-6/battery-light-problem/#sthash.AmszOCJv.dpbs which shows that the wire im looking at just seems to be the warning light wire? any help much appreciated!

[Chrispb]

Hi there
Did you have this problem prior to changing the battery and alternator? is the 13.7 volt reading immediately after the light coming on and is this reading with consumers on like headlight heater blower etc because it looks like it's just stopped charging, I would expect the voltage to drop to nearer 12 volts or lower with consumers on and no charge.

Iv'e not heard of any problems with the MK3 fuse box by the battery but may be worth a look at the connections there for corrosion.

[wilcoxc]

Thanks for the reply!
I didn't have this problem at all beforehand. Basically what happened is i had a small fuel leak on my injector leak-off which got into the alt and killed it, then i ran the battery down. Got leak fixed, new battery, new alternator, but now the light still comes on sometimes!
When i start the car, it either puts out 13.7 volts, which then causes the light to come on after 15-20 secs OR it starts up and puts out 14.6 ish and no light comes on. the 14.6 actually goes up as i switch on blowers, heated windows etc.

[johnnyroper]

Sounds similar to a fault I had on a transit connect,if it works the same they have smart charging on them and it was common for the wiring to alternator that controls the smart got corroded.
As it is only since alternator change I would check the plug for signs of corrosion/damage if all ok then new alternator could be iffy. Was it a genuine alternator or a recon?
Also what battery you got as smart charge needs silver calcium not lead acid.

[mike wilson]

My (one year older) Mondeo has exactly the same motor and alternator setup.  It has done this for the last six years (since I bought it) and is still on the original battery and alternator, at 165,000miles.  There are a few other electrical idiosyncracies as well.  Occasionally the ICE lights do not come on for a while, although everything works.  These things happen maybe three or four times a year - that I notice.....

Try letting it run for about 30 seconds and see if the light goes out.  Mine does.

I put it down to some sort of software glitch in the charge management system and stopped worrying about four years ago.

Edit:  I've just read your post properly and I see yours goes out first.  Mine does not go out immediately.  When it goes out, it does not come on again.  So ignore me....

[wilcoxc]

Thanks for the responses!
The new battery is not silver calcium - its an RAC fitted battery who assure me they have fitted hundreds of them on fords with no issues. IF it was the battery, would this not put the battery light on EVERY time? Does anyone know where the 3 wire pigtail is on the alternator as i can only find a single black/blue striped wire.

[johnnyroper]

Silver ones can take more punishment than lead type that's why they should be fitted with smart charging.
You may well have just the single wire set up then as some fords do,I think it goes back to a module and is controlled there. As you didn't have fault before I would suspect either issue with that wire getting damaged when alt changed,poor connection or the alternator is faulty.

[wilcoxc]

I cant seem to find any info on the single wire setup. Strange how it either starts fine and puts out full charge or starts 'bad' and puts out 'default' charge.

[Chrispb]

I the alternator still has a warranty i would certainly get them to test it or just send it back specially if you got it online.

[wilcoxc]

Got it at halfords, had it back twice, both times saying they found a loose connection, but its still happening. Just found this https://www.nxp.com/docs/en/application-note/AN4289.pdf
which seems to explain most of whats happening, seems to be dropping into self-excitation mode for some reason.

[Chrispb]

Think I would be asking for replacement not some sort of repair.

[mike wilson]

Plus, if you do have a smart-charge system, (and all I know indicates that you should) a lead-acid battery will not work with it for long.  All smart-charge means (simplified) is that it can put out a much higher charging voltage than the system designed for lead-acid batteries.  Silver-calcium can cope with this, lead-acid cannot.

This pdf may help.
http://www.valeoservice.com/data/master/webfile/2945759434DDE6E8714173.pdf

[mike wilson]

And some more diagnostic stuff.

http://www.bba-reman.com/forums/Topic56772.aspx

Note that the poster has pins 1 & 2 the wrong way round.

[wilcoxc]

Just pulled an error code- P1632 smart alternator, output circuit
                                      -Activation fault
                                      - intermittent

P1632 smart alternator, output circuit
                                      -No message
                                      - intermittent

[johnnyroper]

Either wire issue between alternator and ecu/pcm but as it's only happened after a recon alternator I would say it's that causing it. As halfrauds keep saying it's ok might be worth getting a decent auto electrician to diagnose and take their report back to halfrauds

[mike wilson]

Are you sure you have been supplied with the correct alternator?  If you have, has it been installed correctly?

[wilcoxc]

As to whether or not it is the correct type and fitted properly i can only assume so. When it does run properly, disconnecting the LIN wire immediate drops output voltage to 13.7ish, re-connect and it goes straight back to 14.7ish. This says to me that the fault is not a break within the wiring, as im only touching the actual connector, not flexing any wire.