Earth Swap Problems - Short Circuit/Arc

[Nancy]

Hi there,

I've got a '64 Morris Minor 1000 (completly standard) and have done the positive to negative earth swap as according to the instructions on this forum a week or so ago.

One note I must make when I was changing the polarity on the dynamo was that even after a few strikes it was still producing a small spark. Once the coil leads were swapped and the battery terminals swapped all seemed ok and the car started (and the red charging light went off)

I came to start the Morris today but have found that there is a major drain on the battery which is first causing the battery to die (was near enough 0V) but also causing a powerful arc when I try and connect a booster box.

Since then I have done the swap back to positive earth (there was still a spark when reverse polaritising the dynamo) and still there is a major arc/short circuit when I am trying to connect the battery terminal on.

Can anyone help?

[Nancy]

EDIT: Right, had a little go at fault finding.

As it seemed like a major short circuit (was causing the circuit breaker in the booster box to trip) I decided to first disconnect the dynamo & the starter and connect everything up but it still proved to be there.

[bmcecosse]

Possibly the starter solenoid is stuck in ? It's not really likely to be anything to do with the polarity reversal. And yes - the dynamo will always give a little spark each time you 'flash' it. Don't worry about that.

[Nancy]

Tried disconnecting the starter (the big black cable going to the starter from the solenoid) and then supplying the starter with direct voltage but there was still an arc.

With the starter motor lead disconnected from the solenoid I again applied voltage to the battery terminals (one to the body and one to the solenoid) and again there was an arc.

Could it be both the starter and the solenoid?

[Nancy]

Also forgot to add,

its a pull start (instead of the key start) if that makes any difference?

[Alec]

Hello Nancy,

I'm having a problem understanding where your problem is?
You refer to a solenoid yet you say it is pull start which doesn't need the solenoid. If you put power to any circuit you will get an arc, that is not a fault, and something that draws a lot of current like a starter motor you will get a good arc if you put a jump lead to it, that is normal.
If you are saying you have a short circuit that is dragging the battery voltage down, there will be evidence such as smoke or something heating up. Is your booster designed to start a car or is it just a battery charger?

Alec

[katy]

If you're connecting a booster to a completely dead (flat) battery, you WILL get an arc, because the charge from the booster is trying to go into the dead battery.

[phurn]

You dont directly connect a booster to the battery anyway! You put The positive on the positive terminal and the negative to the body work!!!

[Alec]

Hello Phurn,

"The positive on the positive terminal and the negative to the body work!!!"

Why do you say that, I can't see any reason,and you wouldn't normally have it switched on before connecting anyway?

Alec

[Nancy]

Sorry guys,

Just to clear a few things up.

The solenoid i'm refering to is just the push-start button (to the left of the battery if looking at it from the front).

The battery was totally dead as if I had left the lights on although everything was off when parked up.

The booster box is a Snap - On booster (1700MAH) with a built in circuit breaker for use when the user has put the connections on the terminals the wrong way round - its that which is tripping if I keep the connection on the battery/body for a few seconds.

When I connect a battery or the booster box (sometimes I just connect the booster and remove the battery as it would trip before any fires happen etc) to the car I am getting a very strong spark such that the terminal has began to start smoking/fizzing as if I was putting a bar across the +ve and the -ve terminals of the battery.

I'm kind of stuck, I cant see what could be causing the short to be that bad (theres no extra wiring on the car, its completly standard). The only thing that has been done recently is of course the changing of the earth, a new exhaust added and the car was raised on axle stands and under sealed.

In reference to not putting both connections onto the battery, I was told that this is due to once the vehicle starting, the charging system would try and charge the booster box (correct me if I am wrong)

[Alec]

Hello Nancy,

you need to split the circuit until you find where the draw is. Start at the starter switch and disconnect the starter motor lead and the other brown cables and reconnect the battery. If it is really flat, then it needs a very slow charge initially to bring it back up. Batteries don't like being boost charged, it's better to trickle charge although your unit specification seems odd, 1700 maH is less than 2 amps (Assuming milliamp hour) so is insufficient to cause any significant arc or fizzing. Is that what the data plate says?

You can't charge a booster and it's irrelevant whether the earth is on the body or the battery as electrically they are the same.

Alec

[MarkyB]

Can I ask why you were doing the polarity change?
Did you fit something like a radio or CD player after you did it?

If so disconnect that first before you try anything else.

[phurn]

Yes they are the same electricly speaking. However a dead battery has a very high risk of exploding, which when your bent over it will make a right mess of your face and hands. DON'T DO IT. Always connect the negative to a good earthing point on your car, away from the battery.

It's a special kind of idiot who runs risks with batteries.

[bmcecosse]

First step - disconnect the battery, and connect the charger to the battery - not in 'boost' mode - does that work? Is the battery taking a charge? I assume you are connecting +ve to +ve and -ve to -ve....... For something to run the battery down - it must be taking current even though you appear to have nothing (including the starter) switched on. #1 suspect for me will be the dynamo control box - remove the cover and inspect the contacts - are they 'welded' shut ?

[Alec]

Hello Phurn,

Nancy's question was about the booster being charged when the vehicle started, and was told that won't happen if the negative was connected to the body which is incorrect.
It is not a good idea to jump start a vehicle with a totally discharged battery.

Alec

[phurn]

The fuel pump contacts could have fused if he didn't clean them sufficiently...

[bmcecosse]

Wouldn't run down the battery....only live when IGN on, and current drain limited by the coil impedance, so no big 'flash'. Control box contacts welded in = dynamo trying to run as a motor -and draws quite a high current as it does so....

[phurn]

Makes sense... easy way to check would be to.take.the fan belt off and connect the battery wouldn't it? If theyre stuck it'l motor.

[bmcecosse]

Indeed it will - unless the earlier efforts have burned it out.......

[MarkyB]

If you've made a change, like fitting a radio for instance, I'd say revisit that first and take it out of the equation, rather than look at other things that cause the same symptoms.
After all, it was all fine before.