Sierra 2.0i DOHC - Busted alternator or faulty indicator?

Hi

The alternator/battery charging light is lit dimly when engine is idle, but gets stronger and stronger as I increase the revs. However, I have measured the voltages at 1000, 2000 and 3000 rpms and the readings dont seem to fit what the light is indicating.

At 1000rpms with heater and light on, it reads 12.23v. At 2000rpms it reads

13.74v, and at 3000rpms it reads 14.00v. Am I just mistaken or is the indicator light showing a wrong warning?
Reply to
Jonas
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I have the same problem on my 405. I'm sure that my alternator is duff though as it has a flat battery if too many things are switched on and I don't give it a decent run. Remember that you should be charging at

13.8-14.4V with no load.
Reply to
yeha

Reply to
Mindwipe

It is quite possible to have the warning light come on as you describe, yet the actual charge rate is ok. You are getting an early warning of failure, so it would be a good idea to drop the alternator into a rebuilder and get it sorted before it lets you down.

MrCheerful

Reply to
MrCheerful

Sounds like the diode packs started to fail. Try an autoelectricians or rebuilder, you won't get a diagnosis without an oscilloscope, if you've got one try picoscopes website for piccys.

Reply to
duncanwood

If you remove the diode pack, on some the individual diodes can be tested with a DVM - they'll read near short circuit in one direction, several hundred ohms in the other.

Reply to
Dave Plowman

it's knackered get it sorted it might be the little electric thing on the back or it might be the alternator itself (they just love being covered in power steering fluid) the way to check on this is to A) tell me what model it is and then B) turn on all the electrical systems at once lower spec cars have a 70A alternator while the ghia and XR (and possibly the later spec(92) GLS/GLX) uses a 90A one make sure you know which one you've got before you go round and chop and change it the battery is also rated accordingly

you can't use one from a different engine as the pulley is different and the bracket is the wrong way round

Reply to
dojj

I'm having problems identifying it without taking the whole alternator out. From the looks of it (comparing pictures) its a Lucas A127, but how do I identify if its 70 or 90A? The car is a Ford Sierra 2.0i (EFI) DOHC CLX/CLI.

Will it be enough to change the brush box or is it something internal? Sorry about my confusion, I'm a foreign student in Edinburgh with a foreign car, and don't know much about cars either.

Due to some rules in my home country, the car starts with lights default on so I have not been able to test the car without headlights on (have to remove a fuse I guess).

What is the price for reconditioned alternators in the UK?

Reply to
Jonas

last time I got a recon alternator, with 12 month guarantee, it was £70 fitted

I know that Lucas used to do an "lifetime" warranty with some of their stuff a while ago but I don't know if it's still in operation

after you've stuck your head into the engine bay you will possibly see a little sticker on the side body of the alternator (the round bit as opposed to the flat ends) which will have either 70A or 90A on it amongst lots of other info it's about the size of a stamp to look hard for it if it's not there then the alternator has already been reckoned at some point in it's life

Reply to
dojj

Ok, confused again.

Started engine, revved it up to 3000rpm, steady 14v with full heatfan and lights on, still glowing charge light. Then I dropped it to idle 1000rpm, and it reads 14.2v charging but the charge light glows dimly. Will the alternator light actually tell me that it is about to stop working but is currently still doing its job?

Just want to be completely sure that the alternator is actually bust.

Reply to
Jonas

it might be the pcb on the back of the instrument cluster swap it for another one and see what happens a tenner from the scrappy and cheaper than the alternator

Reply to
dojj

Duff alternator. Got a recon incl fitting for =A342.

--=20 Conor

Hi. This is my friend, Jack Shit, and you don't know him.

Reply to
Conor Turton

I had this on a Cortina Mk 5 years ago, and had new alternators about every

11 months until I found it was caused by tracking on the connector plug, which then burnt out the alternators. Changed the plug and it was then fine.
Reply to
TimM

I think the connectors are bolt on for the alternator mentioned, however same thing applies, bad connection could give problems, although less likely.

MrCheerful

Reply to
MrCheerful

That's almost certainly a duff diode then. There's a Lucas centre in Edinburgh

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or you can try searching Yell.co.uk for car electrics in Edinburgh. Well worth ringing round, IIRC the diode packs are just over a tenner & require a big soldering iron,

Reply to
duncanwood

Ok, seems that popular oppinion says its a duff alternator (diodes) so I will replace the alternator. I tried checking the alternator for the "stamp" that had the model no. and if it was 70 or 90 amps, but the only stamp I found was completely blank. Can I measure the output of the alternator without dismantling it? i.e. amperemeter

Thanks for all the replies

Reply to
Jonas

If you can find a large DC clampmeter. Snag is as it's already dying it'll probably underead. Do you have the fastclear windscreen? That always gets a bigger alternator.

Reply to
duncanwood

get the bigger one just as a matter of course :) you can always change the battery later on for the winter :)

Reply to
dojj

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