Uprated alternator

[stewartdjones]

I have a (believe to be) 35 amp alternator fitted to my Cabrio which is fitted with a 2L twin cam DOHC Ford engine. It was purchased during the build in 2006 and has a QH ref FRA687
When normal running during daylight hours the alternator works fine, but when I switch on the headlights as it gets dark, the voltmeter starts dropping down towards Just over 11 volts.
I Don't want to be caught out during the winter.
It is mounted on the near side off the engine low down with a multi tooth belt
Does anybody know off an updated alternator to suit or does anybody have any ideas?

[lil_red_roadster]

Re: Uprated alternator

A quick google suggests FRA687 is a 55A unit.
Should be plenty if it and the battery are both in good order I would have thought...I'd start with having both checked both over, plus a sanity check of the wiring/earths.

[davidmartin720]

Re: Uprated alternator

I had the same problem with my Hunter, a local Battery maker, repairer of alternators/dynamos, reconditioned my alternator for around £30-£40. turned around in a day, no problems since. David.

[stewartdjones]

Re: Uprated alternator

Thanks for that, I recently fitted a new larger capacity battery and have checked the earths, no issues there.
Did also carry out a charging test in situ and appears to be OK.
But why does the volt meter drop from just under 13 volts (normal) to 11volts? Is it me worrying to much?

[stewartdjones]

Re: Uprated alternator

Thanks, I might take the alternator off and get it checked, I do have a local outlet who carries out repairs as well.

[milliemarlin]

Re: Uprated alternator

I had a similar problem with my Cabrio (Millie) it turned out to be the battery. I guess since you don’t mention it that you don’t have an ammeter. If you did you could check that the alternator was giving a good charge. Does the voltage stabilise at higher revs? Is this is only a recent occurrence and you have changed the battery checked the wiring it only really leaves the alternator as failing.

Just out interest how much bigger capacity is the battery? Could the alternator be struggling to charge that? Was the battery purchased from a reputable dealer?
Paul

[stevejgreen]

Re: Uprated alternator

Check the size of the charging cables. Consumption can be dropped by using LED lights front rear and side, it's only a few watts each, but it makes a difference. Headlights if they can be convertedhave a bigger impact.

Lots of questions about the battery and charge rates, you don't quote numbers, but I would suspect the existing alternator first.

[chris_cussen]

Re: Uprated alternator

As a ball park figure each headlamp (60 watts) will take 60/12 amps = 5 amps so even if you have spots on as well main beam should use about 20 amps.
Sidelights will add up to about another 5 amps
Heater on max is about 8 amps and windscreen wipers about 5 amps too and 5 amps for the ECU/Coil. I doubt you have much more than that wired up unless you have a megawatt sound system, so your total consumption should be, at a maximum, 20+5+8+5+5+5 or 48 amps, however if you are on dipped beam, heater on a gentle blow and no wipers the total draw would be in the region of 25 amps.
So if you are seeing a drop in voltage with just headlamps on it means your alternator is not really up to the job, if it is rated at 35 amps then it really needs repair or replacement.

[scott h]

Re: Uprated alternator

It may sound obvious but have you checked the drive belt tension? A slack belt would give the symptoms that you describe of charging voltage drop under load.

[stevejgreen]

Re: Uprated alternator

It may sound obvious but have you checked the drive belt tension? A slack belt would give the symptoms that you describe of charging voltage drop under load.

It apparently has a multi tooth belt, from the first post, so I doubt that is an issue unless the teeth have stripped off.

[burnside]

Re: Uprated alternator

Bear in mind that alternator is a recycled unit QH never made alternators but they did sell remanufactured units so the reg and rectifier may well have had a life before ending up in that unit, that side of their buisiness is long gone I am sorry to say.
I would be inclined to check the output to see what it is charging at and in the long term replace it with a more recent unit Lucas, Delco or another premium brand of remanufactured unit

[chris_cussen]

Re: Uprated alternator

DOHC EFI engines have a grooved belt, not one with teeth so it *could* be slipping.
However that 'standard' DOHC alternator is rated at 60 amps. Don't forget the orignal Serria it came from had heated rear screens, electric windows and other bits and peices requiring power and it is most unlikely you are getting anywhere near the maximum current draw from a standard alternator with the lights on.

If you are seeing a voltage drop when you have electrical load increasing it really does point to a duff alternator

[burnside]

Re: Uprated alternator

THe QH alternator is not a standard original equipment it is an aftermarket reconditioned unit hence the reduced output as the OE unit should have been Bosch or Lucas/Hella
Grooved belts are more efficient than notched or v belts and generally are not so prone to slippage

[stewartdjones]

Re: Uprated alternator

Can anybody with a Cabrio fitted with a 2.0l DOHC let me know what alternator is fitted (make and type).
Many thanks for the comments and advice that have been written, it has helped, upon checking it is a 55amp unit and is was subject to various leaks coming from the radiator outlet situated above. I have checked the wiring, earths and battery and all is ok, hence the request above.
Again many thanks for the comments.

[ggrum]

Re: Uprated alternator

As far as I can see mine is a Lucas LA356 24024 LAFDC. Don't know what the rated current is but it seems to do the job.