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MG Midget and Sprite General - Alternator Wiring problem!

Hi All, right as the title says I'm having a bit of trouble with the wiring with my alternator. I have just put a new(good second hand) wiring loom in the engine bay and under dash as the last one was blown. Now i have just basically done a swap over like for like with the wiring diagram whilst taking out any extra wiring that has been added along the way. One of the previous owners has already done the conversion from dynamo to alternator so i copied the way that the wiring was connected instead of using the control box (please see picture below).

So here is my problem: When the engine is running the main part of the loom along the right side of the engine gets really hot! Firstly are the wires connected together correctly? Secondly could this be down to a bad earth? or Thirdly is the wiring just not up to an alternator conversion?

Please forgive the bad connections as they are only temporary until i figure out what is the correct order to put the wires together.

Any help or pointers would be much appreciated.

J A Butterfield

It is impossible to determine how that is wired from the photo. It would be wise to get someone from your local area to sort it for you it ought only to take a few seconds to check it out and correct any faults
Robert (Bob) Midget Turbo

Yeah the picture is a bit rough! Who would you suggest? an Auto Electrician or an MG enthusiast?
J A Butterfield

The wiring IS up to an alternator conversion, many of us have done so easily and without problems.

As Bob says it is impossible to work out exactly what has been done, you need to get expert advice quickly

hot wires

are only good in electric fires!



If you want to start again this diagram will give you some guidance

You need to supply power to the wiring loom from the solenoid via the fuse box

You do not need the control box if you sort out the supply to the fuses as per the diagram

There are lots of quite similar versions of "ways to do the job" around the interweb, have a looksee for a method that suits you

Bill 1

Right, I have searched the web and found endless contradicting ways to wire up the alternator so I eventually whittled it down to what I thought looked the simplest!!!

What I did:

Alternator end (AC Delco): Connected the thick Brown with yellow trace to the + post and the thinner Brown with green trace to the D+.

Ex Control box end: connected both Brown Yellow trace wires together, both Brown wires together, Brown with Green trace to the fuse box on same fuse as purple(horns)+ Brown and screwed the Black to earthed body.

So after scratching my head allot and looking at the wiring diagram whilst reading the pages of instructions I still have the following problems:

1) Still don't trust the way I have wired it all together as I'm obviously electrically dyslexic and need instructions made for Johnny aged 5!

2) The ignition light is permanently on when the battery is connected with or without the key in the ignition!

3) When I connect the battery something clicks inside the Alternator!

Would any of you out there be able to offer me your thoughts or recommend a good auto electrician in the Essex area?
J A Butterfield

Whereabouts in Essex are you?
Graham.
Graham P 1330 Frogeye

I'm in Harlow, near the M11.
J A Butterfield

Please have a look on the MGA Guru website - I know it's for A's - but - it's full of useful information laid out clearly - and simply! A great resource, and possibly way better than anything that has been found for the Midget :(
rachmacb

I'm in Chelmsford, should be able to give you a hand some time over the weekend,
Graham.
Graham P 1330 Frogeye

That's a very generous offer Graham and much appreciated but I'm working this weekend! But if the offer is open for the following weekend i would be very grateful of an expert eye! I would obviously supply endless cups of tea and cheese n pickle sandwiches!
Jed Butterfield

Jed

Here is my email address. rjwelchmidgetataol.com change at to @ naturally

Which car do you have?, from looking at the photo you have a 1275 MK111 around 1971/72? Let me know what you have to my email address and I will send you the simple diagrams you need to sort out your conversion

There are probably at least 3 ways to install the new wiring and I will gladly send you all 3 so you can simply work out which you need.

Take my word it is really simple with the right help.
Robert (Bob) Midget Turbo

It must be at the ex control box wiring end, ah it is

+ is right for charging power out at the alternator

Brown green thin wire is the right wire for the charging lamp but you do not need to take it to the fuse box at all just make sure the wire runs uninterrupted to the ignition warning light, ignore any other connection with this wire. As you have wired it it is constantly powering the alternator, because the horn is permanantly live

What you need at the ignition light and you can check this with the usual amount of Midget discomfort, is an ignition fed live to the bulb (white wire from the ignition switch to the bulb holder) this wire then goes as brown yellow to the alternator. When you had a control box in circuit it was fed into the C/Box then out to the dynamo as brown green

Taking out the C/Box means you can simply connect the brown yellow from inside the car to the brown green under the bonnet

This ought to then operate the alternator (which needs the 12v supply from this wire to turn it on)

And allow the unhappy busy wiring to relax as the flow is shut off

If you can afford to wait for Graham to pop round fine, if not this is how my car works at present

(although to be awkward I ran a Blue wire to my small (ind) connection on the alternator, simply because a few cars I have seen have used blue as IND wire colours. You can stick with Brown Green :) )

Take up Bob's offer as he can help you very easily

As he says, it is simple, takes longer to describe that to do it when you waffle like me
Bill 1

So from what you have said it sounds like all i need to do is unplug the Brown Green wire from the fuse box and connect it to the Brown Yellow wire's that i have connected together from the old control box? Is that correct?
Jed Butterfield

Jed, the next week end is no problem if you are still stuck!! The wiring on alternators is really very simple so shouldn't take long to sort out. You can email me on graham at endwa dot org dot uk,
Graham.
ps don't do cheese, but drink gallons of tea :+)
Graham P 1330 Frogeye

Yes but


Yes

but check with the info Bob will send you

You need to understand the basic circuit

Power comes into the circuit from ignition switch through the bulb to the ind terminal on the alternator, this earths and turns on the bulb after energising the fields inside the alternator, when the alternator begins to charge the circuit it causes a balance that turns off the light

so connect br/gn to br/ye only and job done

putting the br/ye to the fuse box "lived" the circuit permanantly

Applying power at the w/l allowed the whole ignition powered part of the wiring to become permanantly live

Even when switched off, power coming in downstream so to speak

Check with Bob's diagrams, they will help you
+++++++++++++++++++++++++++++++++++++++++++++

All over the net there are ways to do this basically simple job, the problem comes when you aren't too happy tracing wiring from a diagram
Bill 1

Hi guy's I thought i would post an update!

Firstly i would like to thank you for your patience with a thicko like me!

Thanks Bill for your easy to understand description of the system, thanks Bob for the fantastically easy to follow drawings and thanks Graham for your offer to pop over but i have just come in from the garage and all is sorted now but you are more than welcome if you are in the area to pop in for a cuppa and look over the money pit! I have plenty of other things that need sorting! ;-)



Jed Butterfield

Thanks for the update Jed

I have been wondering how you got on :)
Bill 1

Thanks, Jed, it's always nice to hear when a problem is resolved.
Graham.
Graham P 1330 Frogeye

This thread was discussed between 04/07/2011 and 17/07/2011

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