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MG Midget and Sprite Technical - Electrical Issues - '73 Midget


Evening gentlemen,


As some on you know, I have been having fueling problems that have (finally) been tracked down to be a simple intermittent electrical fault.

I have temporarily rewired the fuel pump to a separate switch, just so I can enjoy driving the car as it's been a while.

I noticed after my latest shakedown that the power seemed to be constantly on, the indicators would work without the keys in as would the reverse lights. I soon realised I'd been silly and powered up the fuse box from the battery, so everything on the circuit was getting power.

I also whipped off the ignition barrel to check the wiring there. I drew a diagram to remind me which wire went where but have subsequently lost it. I have attached a picture of my barrel in the hope that someone will be kind enough to download it and draw on it with MS Paint et al to indicate which feed goes to which terminal.


Once I know this I can start sorting the rest of the (many) electrical issues on my car. These can then fill up this new thread...


Many thanks,
- Richard


R L J Oakley

Hi

this is going to be tough with no terminal identification, but not impossible. Get out your ohm meter, or a test light, and confirm which terminals are connected to each other in each of the key positions:


there should be two terminals that connect together when the key is inserted, and disconnected when the key is removed. These two would be the black (ground) and purple/pink for the key buzzer. If your car doesn't have a buzzer, then ignore these two terminals.

there should be one terminal that connects to each of the other 3 remaining terminals. This one that connects to all of them is for the brown (+12V) wire.
The other terminals are then for:
- auxiliary power (heater fan, radio, etc.), white / green
- "on" power (fuel pump, coil, fuse block, IGN light), white
- "start" (starter solenoid), white / red


I hope this is helpful,
Norm

FYI, here is a link to the Bentley wiring diagram for a '73, pages 374~6:
http://www.spridget-tech.com/service_manual/Appendix.pdf
Norm Kerr

Hi Richard,

Are your terminals numbered on the back of the ignition? If so, give the MGOC technical department a call (unless someone on here comes to your rescue first) and they'll tell you which coloured wire goes to which terminal. They're a nice bunch and sorted me out when i had a similar problem.

Jamie
Jamie Watt

Hi
zooming in on page 375 I can see numbers next to the four terminals that are used on British cars. If, as Jamie suggested, your cylinder has these numbers it will speed up things:

1 - "start" (starter solenoid), white / red
2 - power source, brown (+12V) wire
3 - "on" power (fuel pump, coil, fuse block, IGN light), white
4 -
5 - auxiliary power (heater fan, radio, etc.), white / green
6 -

Norm
Norm Kerr

Thank you guys.

I got the multimeter out and have cracked it. I have a spare terminal that was not in use. Doesn't seem to connect on any key position to the live. But car starts and electrics work.

I am going to slowly start re-wiring the whole car. It's a compete mess and whoever did the looming last was obviuously rather apethetic towards the job.

I think it was the local garage to the lady who had it last. Classic re-spray job leaving most things in, overspray everywhere, even on a 1 pence piece in the footwell. Annoying.

Anyway, I'll use this thread to document the jobs and pitfalls.



Sincerely,
- Richard
R L J Oakley

Thinners will get the overspray off the 1p piece. :o)
Geoff Mears

Richard,
I hate electrics! But strangely, I find re-wiring a very satisfying job. I think it is because there are lots and lots of minor successes on the way, which maintains the interest. I would check out replacement looms. If yours is really bad you may well find that rewiring the lot from scratch can be a lot easier than trying to repair an old loom that has been hacked about.

It helps to take loads of photos to start with so that you can refer back to these later. Its quicker than writing notes and less easy to loose than scraps of paper!

Guy
Guy

Richard just to confirm below is a photo Tony had to put up for me when I forgot to note the connections

Digital camera and note book out before you disconnect anything (not that I always remember, but I usually regret)




Nigel Atkins

This thread was discussed between 16/02/2011 and 17/02/2011

MG Midget and Sprite Technical index

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