Morris Minor Owners Club

Hello

Driving home after Christmas, I noticed my ignition light wasn't coming on. I assumed it was the lamp, and intended to replace it with a spare when I got home.

Then, on the drive back - heater, screen heater, wipers, sidelights on, etc, I noticed everything getting dimmer. I pulled over and swapped the ignition lamp with another, and turned the car off. Oil pressure light fine, but no igniton light. Oh and of course she wouldn't start, luckily I'd stopped at the top of a short hill...

When I got home, I barely had enough power for indicators and brake lights, so I'd lost the entire charge of the battery (I originally suspected it might have frozen inside or someing stupid)

Does this point to a knackered alternator, or battery? What can I try to determine either?

TIA.

obviously not charging, once running the alternator(Take it it is an alternator as you say ,not dynamo) would provide enough charge even with a totally duff battery. When you say no ign light do you mean no light as you switch on before the car is running,I had this and it was a fault in the control unit inside the alternator.the light dosn't have any effect on the charging system it's only there as an indicator that its charging when it goes off., Check tightness of fan belt,you may be lucky,but suspect new alternator will be needed. Charge up the battery and see if it now starts,then if you have a meter check voltage across the battery,this will confirm or otherwise the output from the alternator. If the battery will not charge then obviously faulty.

If you don't have a meter ,or are unsure about how to check voltage most reasonable motor factors will check it for you and advise where the fault is.
The battery will NOT be frozen,not sure what the freezing point of accid is,certainly not cold enough in UK.

I agree, likely an alternator fault, had it a few times from 'A Supplier' (who must not be named...).
I can, however, heartily recommend Accuspark new alternators from eBay (around £39.95, maybe BB classics, search on eBay for them). Mine's giving sterling service, and their service is second to none!

A fully charged battery freezes at around -70°C, so not a UK problem, but a completely discharged battery will freeze at around -10°C, so could be. The moral is to keep the battery reasonably well charged.

The ignition warning light does provide an 'excitation' voltage to the alternator field windings. If the bulb has blown, there is no excitation voltage and it will rely on residual magnetism to start the charging process, which may be enough but not always.

Check that the ignition warning light bulb is good, and if so it does sound like the alternator may have failed.

And invest in an AMMETER !! Most obvious is loose or broken fan belt - I assume you have checked that. And the cable connections are tight at the alternator? Plug not worked loose ??

Quite ^^^wouldn't be without my ammeter. Hopefully the OP has checked the connections as a matter of course, but it is not the first (new) alternator I've bought with this problem, hence recommendation for a more reliable supplier.

Sadly yes - 'not fit for purpose' springs to mind....

I haven't course checked all the wiring. There is no voltage across the lamp holder even when the bulb is removed, when the engine is not running - I figure this is strange? I was aware of the excitation voltage thing and I guess the alternator is receiving nothing.

I'm going to try a different alternator at the weekend as I'm driving to North Wales with another minor, the owner of which has been kind enough to offer me an assortment of spare parts to diagnose the problem!

An ammeter will indeed be a good investment I feel!

I do have a multimeter so how would I check the alternator is working? Or is my lamp issue worth solving first?

bmcecosse wrote:Sadly yes - 'not fit for purpose' springs to mind....

Yep, in fact I think a certain supplier on here has come up many times as selling alternators that are faulty.
I have no specialist knowledge on the wiring of alternators, but it does require an initial excitation, which is provided via the bulb from an ignition live from the switch. So you'd have to have the ign on to see volts there (you mentioned engine not running).
I think you're barking up the wrong tree, the ignition light is controlled by the diode pack within the alternator. Again, while I have no working knowledge of alternators per se, when the diode packs go there is nothing to 'sense' any current mismatch between battery/charge, so your problem as I see it is purely alternator based, nothing more. Change the alternator, it'll work again. Or fit a dynamo, I've kept mine in the boot in case the alternator goes on a cold dark night. Well worth having one in stock IMO.

Ign light bulbs NEVER fail... My alternators all work perfectly well even with the Ign light wire disconnected. Test for working is v simple -rev up and measure battery volts - should be 13.8/14 -then switch on headlights + heater fan - should still be 13.8 volts !

multimeter on V earth lead to earth,positive to positive,start up and look for as above 14volts perfect,below 13 charging fault.

Thanks for all your knowledgable replies, as always.

I know you like hearing people coming back Roy - not sure what you'll make of this.

A new alternator (borrowed from a friend) did not light up my ignition lamp, or charge the battery.

It was, simply, a failed ignition light. I think it was the lamp holder, but when cut out and replaced with minimal rewiring, the battery charged (on my original alternator) and was faultless for our entire trip around North Wales this weekend.

Moral of the story: Check the little and easy things before spending money on the the most expensive solution!

Amazing.... But indeed - thanks for coming back !!

Check the little and easy things before spending money on the the most expensive solution!

Always a good plan