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MG Midget and Sprite Technical - Mk III dies when main beams cut on

The 1973 Mk III that I've owned for 20 years had been sitting unloved for about four years in my garage for a variety of reasons, none of which are particularly reasonable but I digress. We're moving from that house and needed to move the car - a new battery, brake system bleed and jumper cables and the old girl fired right up. I reregistered the car (and a 36 year old car needs no inspection/MOT in this state!) and I've now been driving her around for a week and was testing the lights here in the driveway of our new home. Indicators - check. Brake lights - check. Low beams - check. Main beams - engine dies. No ignition light on dash. Car was stone cold dead. I worked the turn signal/beam dip and got the ignition light back and the car fired immediately. Tap the brakes - dies. For a while it seems that anything related to lighting or the horn killed the car. I wasn't able to tear into the car and troubleshoot that day; tried it the next day and the car fired, lights worked for a while then the symptoms returned, invariably when I used the main beams. But it also seemed to be heat related - I suspect something's heating up and grounding out.

I'm going to go into it this weekend but I was hoping somebody here has seen similar issues and could offer a bit of guidance.

Many thanks and best,

Craig Zeni
Cary NC USA
C L Zeni

I got a brother in Angier NC just outside of raleigh...No he is not mechanically gifted,

My inital guess is your about to have a large car fire, most likely a short somewhere in the wiring loom. So make sure you get a quick battry disconnect and keep the battry disconnected when your not working on it

Look for sharp metal edgs and bad burn spots, broken or cut insulation, and a big thing...Screws in the wiring loom. namly self tapers....it seems this is a somewhat common occurance...think back...did you put any screws anywhere in the car?


Prop
Props Black Hole

No sheet metal screws...the car is remarkably unmodified from that perspective which is one of the reasons I bought it. I've done the Nissan 5 speed and the tube shock conversions but nothing else. It doesn't even have a radio and hasn't for years...

Good idea on the battery disconnect - I'll pull the positive cable off until I get a disconnect.
C L Zeni

when the car dies...how dead does it go...LOL (Sorry), I mean does nothing work, like there was no battry is installed...or does somethings/anything work

Prop
Props Black Hole

It's 100% stone dead. Nothing works. No starter, no electrical of any sort...as if there's no battery in the car.
C L Zeni

Check the connections on the battery and solenoid first:

- battery +ve and connection to solenoid
- battery -ve connection to earth
- solenoid battery post nut reasonably tight; this also has fat brown to loom
- check fat brown on solenoid makes good contact and hasn't deteriorated.

BTW - if you can relaibly get the car into this state, you should be able to trace the +ve volts from the batter, through the solenoid to the fuse-box where the fat-brown joins. Tell us what you see.

A
Anthony Cutler

Don't understand where Prop is coming from but I have to agree with Ant, sounds like a bad earth on the battery/ engine / body or a poor battery connections. It sounds like when the failing connection is "loaded up" then the connection goes open circuit, classic symptoms
Robert (Bob) Midget Turbo

SORTED!

I took the wires/cables off of the starter relay earlier today, gave them all a good cleaning as well as the battery connection. I turned on every electrical item in the car after it was good and hot under the hood - no issues. Drove the car around for half an hour - no issues when previously it would have died in about 5 minutes. Thanks to Anthony and Robert for your insights.

And came back from the test drive giggling like an eight year old - there is nothing as entertaining as a midget!
C L Zeni

This thread was discussed between 04/09/2009 and 07/09/2009

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