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MG Midget and Sprite Technical - Electric Short?

I recently changed my starter solenoid as it was no longer working. I also had removed the dash to repaint the cowling.

Initially I have had problems getting the starter to kick over but then started to trace wires on the dash and everything started working. Then I heard a snap and everything went dead.

Initially I had the battery red light come on when I turned the key and thought it was all starter solenoid issues. I even traced the wiring to the solenoid and had current to where the white/red wire went in but no power at the starter solenoid hookup where it goes to the starter motor (No current when I turn the key to start position).

So I first thought it was a bad new solenoid. Now however I am finding that if I turn the key on (just to power) so the battery red light comes on and turn anything on such as the turn signal, fan switch, etc everything goes dead.

My question is am I looking at two different problems meaning bad starter solenoid and some short or somethign else where or would it be all linked together.

Where would one start to trouble shoot when everything goes dead whenever any switch is turned on? Thanks
Thor Patterson-Ritz

battery clamps - especially the earths.

What you are seeing is a high resistance somewhere in the system, with low current draw you get enough amps thru the resistance to run the lamps, turning anything else on draws too much current and it all goes dead.

your tools for this ought to be a lamp on some wires. Connect the lamp across the terminals of the battery - switch on "stuff" - does the lamp stay on? no = dead battery

yes-> connect the lamp between the earth terminal and the car, test again - does the lamp switch on? yes = faulty earth to battery

no-> connect the lamp between the purple wires from the fusebox and the +ve terminal, test again - does the lamp come on? yes = fault between fuesbox and +ve terminal

no-> connect the lamp across the purple and green wires at the fusebox, test again - does the lamp come on? yes = fault on the ignition switch or dirty connectors

no....
Will Munns

hey thor,

what car year and model do you have????

considering a good mid-range of common years for the midgets, my guess its the big fat brown wire has a short, easy to do where it comes thur the firewall and have a deteriated rubber gromment, if you got a gen. perhaps a wire is having a problem on the regulator box.


I would defintly disconnect the battry, to avoid any chance of a fire....(there are multiple reasons people get nervous when I put on my Mr. electrician hat...with the words "sparky" written in flaming red across the top.)



prop "By the power of Thors hammer..." Propster
Prop

Ok I have worked through the following:

i installed a new battery and fully charged it just a week ago. I've placed it on the charger and its fully charged at this point.

When I connected the lamp between the earth terminal and the car, lamp remains off

When I connected the lamp between the purple wires from the fusebox and the +ve terminal, the lamp stayed off.

When I connected the lamp across the purple and green wires at the fusebox, test again - the lamp came on = fault on the ignition switch or dirty connectors.

So I switched to different ignition switch from my 1275 parts car. Had the same experience = Power on until I turn key to starter position then entire system goes dead. So my guess is that the first ignition switch isn't bad but something else.

I've traced the white/red wire that hooks to the starter position and tested both current and integrity up to the starter solenoid. I have it but not beyond which I would expect until I turn the key to the start position. The problem is once I turn the key the entire electrical system dies. So could a bad starter solenoid at that connection actually kill the entire car circuity? I don't even get power at the fuse box once the starter key is turned.
Thor Patterson-Ritz

in a word - nope


The test has to be done with the ignition on and reasonable power draw from the ignition circuit, such as brake or reversing lights
Will Munns

have you tested the starter to make sure its okay, will the engine turn by hand,

Were you able to trace that big fat brown wire out of the regulator box....if that wire is cut or shorted, or pinched...nothing works...period.

that being said, we still dont know what you have so the wiring schmatic is up in the air at this point.


prop
Prop

>Now however I am finding that if I turn the key on (just
>to power) so the battery red light comes on and turn
>anything on such as the turn signal, fan switch, etc
>everything goes dead.

this statement rules out the solonoid as the problem (at least the main problem) you need to get the car into the ignition on - no lights state described here before you start digging
Will Munns

Sorry about not stating model and year. It's a 1975 1500 series.

I did try to kick over the starter by touching the two brown connections on the starter solenoid and it did turn the starter motor over. However I did find that the battery most almost complete drained this morning just because I hadn't disconnected the battery so there has to be some power drain somewhere.

So how do I start to isolate the bad wire? Is the fuse box a good starting point?

Thanks again for helping me figure this out.
Thor Patterson-Ritz

I will kindly with draw my input, as i know nothing about 1500's....

It sure sounds like a dead cell in the battry to me, I know from past experiance they can go really fast, when they go, most of the time about 3-5 days tops, take it to a battry shop and have them test it. even though it shows there are still juice in the batt.

prop
Prop

I am pretty sure its not a dead battery cell. Just replaced it as I thought that was the problem initially and the battery wouldn't keep a charge.

What I discovered yesterday was that the new battery went dead quickly if connected to the car's terminal cables and I noticed that if I had the terminal cables hooked to the battery while charging it I could see the battery actually being drained still further, even with the charger on.

So I think I should approach this by disconnecting everything from the battery/solenoid starter, right? Disconnect the Brown wires that connect to it:
1. brown wire to fuse box
2. brown wire to light switch
3. brown wire to Alternator
And
4. the white/red wire that connects ignitiion Switch
5. and finally the white wire (not sure if there is an additional color on this wire or not) that is opposite of the white/red terminal hookup.

Then I think if I only kept the brown wire that connects from the battery to starter solenoid attached I should be able to see if any drain occurs. If so I would know its between the battery and starter -correct?

If that works I should slowly add 1 wire at a time back onto the starter solenoid to see where the drain starts to occur. I can then begin to work up the wiring sections to isolate it. How does this approach sound?

Also can I use a voltmeter to detect a drain on the system? If so, how?

Thanks for the help you all have offered me.
Thor Patterson-Ritz

Hey Thor,

That sure sounds like a good plan to me...

prop
Prop

Well I thought I would share that I finally found out what was causing the problem. My friend Matt come over to help figure this out and while he was looking in the engine bay he had me try to start the car.

He saw a spark jumpt from the oil pressure gauge tubing across to the metal mounting bracket where the speedometer lower and upper cables join, it's a 1975 model thing. Strange thing was that there was no electrical components near any of this so I thought until I traced things back under the dash where I found the cause.

The cable that runs from the vent control dial to the heating housing had become wedged between the speedometer's lightbult metal housing and it's power line. This in turn had the oil pressure tubing laying on it at times thus causing the on and off again problem as the metal tubings did not always contact each other.

Wow has this been an adventure I hope never to repeat. I don't think I would have ever found it if I didn't have another pair of eyes looking in the engine bay while I cranked the car over.
Thor Patterson-Ritz

This thread was discussed between 15/07/2008 and 21/07/2008

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