Morris Minor Owners Club

Hi there,

When I fitted an electrical sender for a temperatur gauge I was stupid enough to damage the alternator by spilling some water over it. I had the alternator covered to keep it dry when I opened the blanking plug but just after taking the cover from the alternator there was some more water spilling out of the zylinder head.

I only had the alternator for some months and just don't want to exchange it again.
As you can get all parts for the alternator separately and I have found a nice series of videos on rebuilding an Lucas ACR Alternator (http://www.5min.com/Video/ACR-Alternato ... -265523913) I thought I might give it a try.

Has someone got an idea what might be broken?
It has to be at least one of the electrical parts.

The alternator is still in the car and I keep Percy running by charging the battery every night with a battery charger.

I'm looking forward to your ideas.

Thanks

Achim[frame][/frame]

Hello Rotgnom,

I think you were unlucky as they can tolerate the odd wetting. A simple check is to check the brushes, make sure they are free in their holders. Is your ignition warning light working?

Alec

Hello Alec and all others,

no, the red ignition light is not shining. When I switch on the ignition the orange charge warning light shines and stopps shining as soon as the engine is running.

Thanks

Achim

Hello Achim,

the ignition warning light is red, the oil pressure warning light is orange. If the ignition warning light is not on, the alternator probably will not charge. If you disconnect the alternator wiring plug and switch on the ignition, then check for 12 v on the thin brown\yellow wire. If that is zero possibly the bulb in the headlamp needs replacing?

Alec

In daily use the alternator takes a fair bit of abuse and I'm sure some water gets into the alternator without causing any harm. You seem fairly ceratin the alternator is broken but also check that everything is connected properly and you haven't by accident pulled any connections off when fitting the sender and guage. My apologies if you have already done this

I can't see it being a wee drop of water - and the ACR works just fine with the red light wire disconnected. Check the main cable connection is good - and as already suggested - check the brushes for sticking and /or worn out. The centre one rarely wears - but the one running on the outer track wears down more quickly.

Hello BMCE,

some ACR alternators may work with the charge line open circuit but it is not a ceratinty and should be corrected if that circuit be defective. You must agree that having the warning light is very useful to day to day running to warn of a lack of charge?

Alec

Hi there,

Percy is on exebition at the stand of German Morris Minor Register at the Techno Classica in Essen for a few days. As the car is parked in one of the exebition halls no one will realize the broken alternator.

I will check the alternator and the wiring next week.

Thanks

Achim

The rotor on an alternator is energised through the ignition warning light. If the light does not illuminate when switching the ignition on, the alternator will not charge, or if it does it will be very very unreliable! I would check the circuit from ignition switch through the ignition warning light to the alternator. Does the ignition warning light work if you remove the plug from the alternator and ground the small connector?

If it doesn't, then it should and needs to be corrected. Once you get the ignition warning light to work, then hopefully the alternator will charge again.

Hello Richard,

that's a good point, because I had the speedo out to connect the temperature gauge at the voltage stabilieser. I will check the ignition warning lamp as soon as Percy is back from Techno Classica.

Thanks

Achim

Richard - it DOES work just fine - with the small wire disconnected (or broken in my case!). My ammeter showed it was still balancing the battery nicely - with lights etc on or not - perfect balance, no under charging or over charging. It is of course handy to have the light - but not essential.

If it was plain water that spilled on the alternator, it shouldn't hurt it. But, if it was a glycol anti-freeze solution, the glycol may have gummed up the brushes and/or slip rings.

Hello Katy,

it was the anti-freeze solution that spilled over the alternator.
I shall check the wiring and the brushes and slip rings next week.

Thanks

Achim

Hi there,

Percy is back from Techno Classica and everyone liked him

Now if checked and double checked the wiring of the alternator.

- When I switch on the ignition the orange oil pressure warning light shows and the red ignition light doesn't

- When I start the engine no light is showing

- I took out the bulb of the ignition light and checked it - ok

- I disconnected the alternator wiring plug, switched on the ignition and checked the thin brown/yellow wire - 12,3 V

- I checked the battery with no ignition switched on - 12,6 V

- I checked the battery with the engine idling - 12, 6 V

- I checked the battery with the engine revving - 12,6 V

To me it looked like that something has to be wrong with the alternator.

- I opened the lid of the alternator to check the brushes and slip rings
and realized the regulator was not fixed properly because of a loose screw and had no connection.

There we are - problem solved. Now I've got both warning lights working and nice 14,5 V at the battery when revving.

Thank you very much for pointing the right way.

Achim

Hello Achim,

good to get a solution without an expense, and gain some knowledge in the meantime.

Alec

Great success - well done!

Well done Achim-see you Sunday.
Grüß
Declan

It is of course handy to have the light - but not essential

Roy,

Alternators do not self-excite, which is why they need the separate DC supply to the rotor to create the initial excitation. Once charging, they are self-contained through the voltage regulator circuit. Some will start to charge if the engine speed is increased enough, but it is not reliable, as they have virtually no inherent residual magnetism to kick the process off.

Many years ago, working for a commercial automotive manufacturer, when very low wattage warning lights became common, we had to fit a resistor in parallel with the ignition warning light to get enough excitation voltage flowing to the rotor, without having to rev the engine to do it. The side effect was that the resistor alone would allow the alternator to excite!

Enter 'car alternator excitation' into Google to get as much detail as you could possibly need!

I always believed that Richard - but I can assure you mine worked fine when the wire broke off - I could watch the thing balancing the battery nicely on my ammeter. I didn't bother to do anything about it for quite some time - and it worked well -and without any obvious 'revving' to get it to kick-in. Maybe some do and some don't. It is of course obviously better to have the light.

I've spent the last 3 weeks charging a battery I believed was faulty; the supplier tested it and blamed the alternator. I replaced it with a used one to no avail. I replaced that with a new one - same result, or lack thereof.

I just replaced the bulb in the speedo (ignition warning light) (long story how that got broken) and will post result later, if i find the culprit.

Meanwhile, serious heart-searching has caused us to stop being sentimental about our car ownership. The Morris has to go.