Morris Minor Owners Club

Yesterday eve, the ign light would only go out at high RPM, So...
Today tightened the belt (it was a little slack), ran the car for a bit & then put it on a charger where the battery went up to 13.4v

This after noon, when switching the ign on, light does not light!
Battery apparently not charging either.

Any simple test to see if it is the alternator or some other fault i.e. in the wiring? The alternator has just 2 wires which go into loom & I'm not sure what they connect to...as often, alterations have been made by previous owners
But why would a wiring fault just happen?

Chris

With engine running measure the battery voltage. If you get 13.8v then alternator is charging. If not look elsewhere....If ign light is working but no longer illuminating check the wiring from the regulator box (if still fitted). Also the reg earths to the body so this may be needing cleaning up a bit.

Tests so far:
The battery reading is currently 12.4v engine off

Ign off: at the alternator, the large wire (to the starter solenoid) is 12.4v to ground
the small wire is 0v

Ign on: at the alternator, the large wire is 12.4v (test lamp illuminates when connected) to ground
the small wire is 11.95v (test lamp not illuminated when connected) to ground

So current is at both alternator wires when ign is on, but no red ign light when ign switched on & no charge from alt when engine running.....
Alternator faulty??? but why is the red ign light not lighting up??

I've put battery back on charge for a bit, since the car will need using briefly later this eve.

But no, alternator is not producing a charge to the battery.

Thanks

No regulator box fitted

Just to check the IGn light bulb - earth the small wire while Ignition is turned on - the red light should glow.

Assuming the bulb is ok - it may just be the brushes - easily changed if a Lucas ACR. Or just pick up another alternator meantime and then have a look at the old one on the bench. Regulars on here know I pay £1 for spare ones - but have to admit - not recently.
http://cgi.ebay.co.uk/P74-BRUSH-SET-LUC ... 5d282dddab
Or it may need a new regulator.......http://cgi.ebay.co.uk/LUCAS-ACR-ALTERNA ... 4835e6dd65
Or possibly a new rectifier set........ http://cgi.ebay.co.uk/NEW-ALTERNATOR-RE ... 3ca65e629d
Or a complete spare ...... http://cgi.ebay.co.uk/MG-Midget-Austin- ... 27b62d221a

Thanks for the advice,

I will do that test for the red light tomorrow.
When I took the battery off charge & started up, although the ign light did not come on before the starter was pulled,
as the engine cranked over it came on briefly before she fired up. Strange.

I see what you mean about the alternators on e bay being a bit more than £1

Well, off to the Fox & Goose now
Tomorrow off to the Lakeland Motor Museum in the Traveller with Cumbria Branch.
At least the Traveller just does what it says on the tin...it goes !

thanks,

Chris

Enjoy!

Hello Chris,

if the ignition light doesn't light when you first switch on, due to a blown bulb or a wiring fault, it is probable that the alternator will not charge as it uses the feed from the ignition switch through the lamp to the alternator to give it some voltage to start charging. Once that starts the alternator then builds up to it's regulated voltage. (serviceable alternator obviously)

Alec

No - I proved that's not so Alec. The small wire had broken at the connector in my car - so no IGN light - yet the alternator continued to function exactly correctly, from my ammeter I could see it was balancing lights/wipers etc on demand - and just trickle charging the battery when running with nothing much switched on.

Hello BMCE,

you were lucky, the ignition warning light is designed to start the charging process, which if you look at the ACR circuit is connected to the field circuit. Larger machines (I'm referring to industrial alternators) use the phenomenon of residual magnetism within the field poles which start the build up. There may have been enough for yours to work but that is not a reason to say that it is not required. Residual magnetism fades with time as the poles are simply mild steel so do not retain magnetism for long.

Alec

Well - it worked like that for quite a while for me. Not just the one trip - since it was charging I didn't bother to investigate until I had time on my hands - and in fact was about to change the alternator, assuming I had 'wasted' £1 on that one - when I realised it was simply a broken wire at the connector! £1 saved !! Happy days......
And yes - the dynamo relies on residual magnetism. Although the alternator is a 3 phase AC machine - i'm not so sure about residual magnetism there! I've never seen an electrical drawing of the alternator - do you have one you can post up ??

Here ya go: http://www.greenenergywindturbine.com/d ... ok_ocr.pdf

All you wanted to know about alternators and then some, mostly American stuff but also has Lucas, Bosch, Hitatchi, etc.

Replaced alternator with exchange Lucas unit (bought locally £29)
Charging fine now..
Job done.

Oddly enough, the car seems to run better....or is that just my imagination???

Thanks to all who were kind enough to give advice!


Chris

Could be placebo effect from having poured £29 into it, or more power giving a better spark.
This will warm Roy's heart, thinking of all the money he's saved .

Yes, well, I have to try & draw some comfort from the spend...If I could find some for £1 each, I'd get the bushes etc & have a go at fixing them.
I see someone on Ebay sells recon. kits, bearings etc.