Dodgy Alternator

Post by **johnm** » Mon Jan 30, 2006 10:46 pm

My wife called the RAC to her Traveller because the charging light was glowing dimly.

RAC checked that fanbelt tension was OK and noted 14.3 volts going into battery with engine running fast idle and diagnosed dying alternator (I've had the upgrade some years ago and polarity reversed).

I confess I would have expected more than 14.3 volts of an alternator and so I'm inclined to accept the advice, do others concur and what is the appropriate alternator? I'm away at present and will need to buy one for fitting next saturday.

Thanks as always for any help and advice

Post by **rayofleamington** » Mon Jan 30, 2006 11:58 pm

14.3 at fast idle is not much to worry about.
Check that the voltage doesn't go high when the engine is at high revs (it should reach a maximum e.g. 14.5 volts and then level off completely). If the voltage wanders around and goes high at high revs then you may just need a regulator pack.
If the alternator output is generally poor, then you may be able to fix it with new brushes (often comes together with the regulator).

Post by **Alec** » Tue Jan 31, 2006 7:52 am

Hello John,

the ignition warning light can glow if the alternator is overcharging, it does not always mean lack of charge. Either way can be a problem.
I personally don't mess around with Lucas 17Acrs or the like as they are so cheap to buy exchange. (Or they were last time I bought one, about £30)

Alec

Post by **bmcecosse** » Wed Feb 01, 2006 7:58 pm

14.3 volts is just right! But it probably means the diodes are failing - and there may be some reverse leakage back through the alternator when the car is standing - with resultant flat battery in the morning. The alternator is actually a 3 phase AC machine - with each phase rectified to DC by diodes. 1 or even 2 phases can fail and the beast will still keep the car going ok provided not too much night-time driving with lights on. Best to start looking for a replacement. My last one cost £1 at an autojumble - still working beautifully 3 years later! You need to watch the 'handing' of these (15/16/17 ACR) alternators - when used on Fords (most common use) they were hung on the other side!

Post by **johnm** » Fri Feb 03, 2006 6:45 pm

Many thanks bmcecosse, job for tomorrow morning I think. The car is doing a lot of miles at present so the battery is fully charged and certainly doesn't leak away over night yet!

Post by **johnm** » Sat Feb 04, 2006 11:21 am

Curses!

Alternator replaced and red light glows as bright as ever!

I'll check whether anything is happening with volts when Mrs Milner returns from the shops.

There are two wires attached to the alternator, one thin green and brown onto a small spade and one large brown and cream on the further away of the two big spades on the alternator, there's nothing connected to the middle spade.

The other end of these is nowhere to be found. they just disappear into the loom.

Help!!!!!!

Edited to add I have now ensured that I've got 12 volts between the little wire and battery earth when the ignition is switched onand I seem to have 12 volts between the big wire and battery earth with ignition off. I assume therefore that little wire energises the alternator when ignition is on and big wire is connected to the battery so as to receive charge.

For my next trick I'm going to see if there's any reliable volts above 12 between the big terminal and battery earth when the engine is running.

Could my new alternator be faulty???

Post by **chrisd87** » Sat Feb 04, 2006 12:29 pm

I had a similar problem when I first fitted my alternator, and eventually the battery went flat.

The actual fault with mine was not the alternator at all, but the wiring. I hadn't got a good enough contact with the solenoid terminal where the large wire attaches - resulting in not enough current getting through and a dimly glowing red light.

Perhaps you should check and clean the terminals just to be sure.

Post by **johnm** » Sat Feb 04, 2006 12:45 pm

Thanks, I'll have a go at all of them this afternoon. I've actually got the alternator though and didn't seem to be getting much out of the back of it from the big terminal.

Nonetheless it can't be many things can it! There's only an energising current and an output current and if both of those show 12 volts then somethings connected!

Post by **johnm** » Sat Feb 04, 2006 3:09 pm

SUCCESS!!!

It was a dodgy new alternator. I was able to show there was no output at the back. Second new alternator obtained and as a precaution I remade the alternator connections and cleaned the solenoid connection and heypresto no little red light anymore.

Post by **bmcecosse** » Sat Feb 04, 2006 5:03 pm

Well done - but do tell who supplied the faulty alternator - so we can avoid them !

Post by **Matt** » Sat Feb 04, 2006 5:05 pm

Wouldn't naming and shaming be against the T&Cs?

Post by **johnm** » Sat Feb 04, 2006 5:21 pm

I think naming and shaming would be out of order! I think it was just one of those unfortunate things. The supplier had two or three in stock and exchanged the first one for another without demur and problem fixed.

Post by **bmcecosse** » Tue Feb 07, 2006 8:03 pm

Surely naming and shaming must be ok if it is strictly factual! In this case - new alternotor did not work, no ifs buts or doubts - it just was not working !

Post by **KirstMin** » Wed Feb 08, 2006 11:26 am

Naming and shaming is against the T&C's UNLESS the company in question is Halfords; and then, 'apparently', because they are a large, chain store* it is perfectly OK to say whatever you like (going as far as changing their name to a derogatory version of) even if you haven't actually had anything go wrong with ANYTHING you have bought from there. This is my interpretation of the T&C's judging by previous posts.

:D

* not that I like chain stores

Post by **rayofleamington** » Wed Feb 08, 2006 12:03 pm

Well spotted KM ;-)

Post by **KirstMin** » Wed Feb 08, 2006 3:33 pm

rayofleamington wrote:Well spotted KM ;-)

I'm a quick learner!

Post by **johnm** » Fri Feb 10, 2006 6:35 pm

OK you win, the OEM supplier was AC Delco