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MG Midget and Sprite Technical - Alternator faulty?

I've not been on here for ages, so hello again.
My car has been in storage for the last 3 years, with just an annual trip-out for an MOT, I've kept it running but not used it. (Young family, house extension, no time, etc. etc.) Anyway; yesterday I took it out for a spin and noticed that the Ignition light was on contantly whist driving, I checked the obvious Fan Belt, that would have been too easy, so I'm thinking duff Alternator; the light is very dim at idle, but increases in brightness as the revs increase, any opinions before I swap for a new Alternator?
Funny how things break when they're not doing anything!
T Holdsworth

1st take the car to any parts store, they can check it for free in 10 minutes.. and tell you if itz good or not... some stores you have to bring the alt in off the car for testing

m not sure if you have the mechanical regulator box, if so, it may need to have the contacts cleaned up... use a glass pen from a camera shop works best

Check the wire connections... if the battry was always hooked up, it could be corrosion INSIDE the insulation... so physically remove the wire to see inside the insulation for the mint green color powder

Because the battrey is used so little, id have it tested also for a dead cell, battries dont sit well over time, they will go bad quick because of how they are designed... charge and discharged alot over time is how they like to live

Might be time to find a neibor, friend or family member to drive the car once a week for a couple of hours if you / the wife cant... it will certianly save you huge amounts of cash in the next year or 2 in restoration cost

This is the 1st of many issue to come if you continue to let it sit unused

Not driving these cars will destory them really fast and the repairs for this kind of can add up to serious cash very fast.

Use it,

find someone to use it for you on a regular basis,

plan on spending alot of cash and time repairing it

or sell it

Prop
Prop and the Blackhole Midget

How old is the alternator?

Have you run the engine without the battery in the car?

Give it all a good clean.

After checking that all the connections are good and clean, and if it still isn't working, sounds like the rectifier could have a blown diode or 2.

Take off the black plastic cover, remove the brushes and inspect those. Clean the slip rings if needed. Test it.

If that doesn't fix it, then if you fancy playing with a soldering iron, buy a new rectifier and solder it in.

If not, but an exchange or new alternator.
Lawrence Slater

Ill ask the next obvious question...

How do I check and test the rectifier....??

The only way I know of is to take an old mercury thermo, and shove it up you butt for 5 minutes while remembering not to sit down and injecting your self with a bad case of mercury poisoning into your fun hole

Maybe lawerance has a better method...

Prop
Prop and the Blackhole Midget

T Holdsworth,

Is the alternator connector a push on type with 3 spade connectors, if so I would start by pulling the plug and re-inserting it as that helps to wipe away any oxidation that may have occurred and which may be causing problems, also check that the connections grip tightly. Personally I dislike the the alternator spade connections with a vengeance as I've always found them prone to oxidation problems which would show up every few years and require attention like cleaning and squeezing the connectors. As they oxidise the contact resistance goes up and causes heating which causes more oxidation, a viscous circle. Never had a problem with the alternators with stud connections on the back, just the spade connection ones but I suspect the spade connections help assemble the car a bit quicker therefore more cheaply on the production line .
David Billington

a very little dab of electric contact lube after cleaning can help to keep moisture and crud at bay

don't be tempted to buy a new 3 section plug as they're poor quality - or they were when I bought from two different sources and got the same one
Nigel Atkins

Nigel is right about new three terminal plugs

awful things

I use two yellow (big) spade terminals and one blue (medium) terminal which I crimp then solder the wires to, then fill the spades with electrolube from Auto Electric Supplies in Tenbury Wells

From looking at their website (no I'm not a company stooge) they sell one called Contralube these days

But there is no way to know if your alternator is working or not unless you can measure the voltage at the battery with the engine running

A working alternator should be delivering 13.5 volts (ish, it may be slightly higher or lower but 13.2 minimum)

So you need a VOM (meter) that lets you check voltage before you second guess yourself
bill l

Not so difficult. A 12V test light will give you a good idea of what's going on.

I'll beat nigel to this link to John Twist.

http://www.youtube.com/watch?v=TMgRfToSiLY

You can test the field and stator windings for continuity the same way.



Lawrence Slater

Hi T,
A new one from Mini spares is only £43.49. Other places may be cheaper if you like dealing with companies that rhyme with Toss.
Yes you should check the output with a volt meter and that the connections are all clean, but if you do not have time or skills to diagnose and repair your existing one, a replacement should not break the bank.
A simple job to replace and you get a nice new shiny bit in your engine bay.

Dave

Dave Brown

Or you could do what 92% of the population does when testing an alt

Take it to auto zone parts store for a free 10 minute test to determine if its good or bad,

Then if bad spend the extra 10er for a rebuilt alt with all new guts and avoid the 2 hours it takes to rebuild and hoping you did it correctly the 1st time because when was the last time you used a soildering iron and how well did that go

And dont forget those electronic tools you have buy, $25 dollar volt tester, $10 test light, $18 soidering iron, $8 soilder wire, $7 tub of flux, $7 magnifiy glass, $7 work light, $15 soildering work station

The good thing... you will have all this equipment to do the next alt in 15 years provided you keep it all togather in one place your sure to never loose it... and can actually remember where that place is in 15 years from now...btw, how old are you? And you will be how old in $15 years

Yepp... proof there is always a very hard way and expensive way to do something thats very simple

Prop
Prop and the Blackhole Midget

£43.49 vs 6 quid, if all you need is a regulator or rectifier. I think the effort is worth it to save over 35 quid, and it's satisfying, as someone said on another alternator thread.
Lawrence Slater

In principle, I agree with Lawrence (again!). But it also depends on how much time you cam afford to spend doing these things, and what else you might prefer to be doing with that time. Which rather contradicts, in Lawrence's case - a long discussion he had a year or two back when he was proclaiming the merits of him sitting in the sun doing bu66er all!

And the same logic that says buy a recon alternator for £43 rather than replace some £6 parts because a) its cheap and b) there is a long list of tools and equipment that you need to have also bought (Prop's argument) would also say buy a cheap new Korean car with a 100,000 mile guarantee because its a) cheap and b) you don't have to own any tools at all to be able to run it.
Guy Weller

Yer pays yer money and takes yer choice!
All depends on your technical ability, tools at hand, inclination, amount of spare time, list of other jobs to do, priorities, satisfaction gained from what ever option you decide to take etc. as to what option you take.
Just putting up other options.

Dave
Dave Brown

Certainly Dave. And I think your argument of "Yer pays yer money and takes yer choice!" is a far sounder one than trying to persuade others on either grounds of logic or different perceptions of what is individually "worthwhile".
Guy Weller

Guy and dave,

Those are very good thoughts, buts lets just be very clear, all thinking aside

My way IS the right path.....hahaha

Prop
Prop and the Blackhole Midget

Dangerous Prop...
That is what they are thinking in Iran and Syria.
Dave Brown

Haha...

dave, your on today, I didnt know if anyone would make the connection

Good job

Prop
Prop and the Blackhole Midget

I've always found it good practice to understand all the little bits that make up the whole machine. If you have the time play with the parts.....

Prices are always going up and a little knowledge can save you some money. I'm with guy and Lawrence on this one......Learn what you can...

but there's always more than one way to skin an alternator....:-)
Steven Devine

I did say in my first post in this thread ---

" -- if you fancy playing with a soldering iron, buy a new rectifier and solder it in."

The operative phrase being "if you fancy", covered the amount of time and ability available. ;).

But Guy has me on one thing. I'm always torn these days between fixing, or doing anything at all, and sitting in the sun with a cold one. It's a struggle. If I fix it myself and save money, more money for grog. If I sit in the sun several sheets to the wind, I can't fix it.

Unless I drink in the sun, whilst at the same time fixing whatever needs to be fixed. lol.

I often "fix" the world, whilst imbibing in the sun. LOL.
Lawrence Slater

This thread was discussed between 16/06/2014 and 19/06/2014

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