Mazda 121 - 1.3 - 1996 - Draining Battery

Honest John Back Room » Technical matters
What is life like with your car? Let us know and win £500 in John Lewis vouchers | No thanks
View Threaded
Fri 25 Feb 2011 16:55
Mazda 121 - 1.3 - 1996 - Draining Battery - Gusty

Its the Ford Fiesta clone. P Reg, 1.3, Auto, my wifes car, 47k miles

Have a draining battery, from full to empty in a week when sat on the drive. This is the second time in 4 weeks. The car is not used much, but we have had it for 2 years and this has just started happening.

Checked the obvious, interior light, radio, side-lights etc, etc. All off

When I put a multi-meter acoss the live battery terminal to earth, it indicated a full short, which is a little worrying... Should that happen, surely that is dangerous?
Disconnected the alternator, short still there.

There are 3 wires going to the positive terminal, a chunking big one that has the battery connection on the end and 2 smaller cables connected to it.
I disconnected the 3 cables and checked them individually.
The Big cable and one of the smaller cables are fine.. no short.
Its the other of the smaller cables that directly earths out, it disappears under the Engine bay fuse box, I guess it the main power source... But I do not know this for sure.

I don't know if it has any bearing, but the Mazda/Ford Handbook says.. When starting the car using jump leads, Connect the positive, but connect the negative to the body work, not the negative terminal.. seems strange.

I have dismantled some of the interior and checked the loom path along the off-side.-- no obvious broken cables.
I have also crawled thro the fuse boxes, nothing blown

I am not a mechanic, or an electrician, but I was always pretty sure that a lead connected to the positive should not also be somehow connecting to the earth system.

Any pointers or Help would be much appreciated. Thanks

Reply | Report as offensive | Link
Fri 25 Feb 2011 18:38
Mazda 121 - 1.3 - 1996 - Draining Battery - elekie&a/c doctor

A short circuit results with a blown fuse or burnt wiring.I don't think you have either here.A battery drain needs to be checked with an amp meter in series with either the main power or earth lead.This means disconnecting either to make the connection.(or a more expensive clamp meter can be used which does not require any disconnecting).Have you had the battery tested?These old Fiesta/Mazda models are very basic and rarely give electrical drain faults.It is possible for the radio to be the culprit even though it is switched off.hth

Reply | Report as offensive | Link
Fri 25 Feb 2011 19:06
Mazda 121 - 1.3 - 1996 - Draining Battery - jc2

It is recommended that the final connection on the car to be charged is not made on the battery so that there can be no chance of a spark exploding hydrogen escaping from the battery as it charges.

Reply | Report as offensive | Link
Fri 25 Feb 2011 21:29
Mazda 121 - 1.3 - 1996 - Draining Battery - Gusty

Thanks for your response..

The Battery was new last summer.

The insulation on the cable that I found earthing-out with the multimeter has obviously got hot, as I was moving it, the insulation was cracking and falling away in my hand.

I am pretty sure its the cable that feeds the under-bonnet fuse box, but I can't trace the wire fully. I need to dismantle more of the car.

I did find that one of the solenoids in the same fuse-box also earths out with the multimeter... but I have no idea what the solenoid controls, again, more investigation.

Going back to basics.. am I correct in saying that one of the cables attached to the positive should not give a fully earthed reading.

Reply | Report as offensive | Link
Fri 25 Feb 2011 21:37
Mazda 121 - 1.3 - 1996 - Draining Battery - Gusty

According to my wife.. breaking news.. the tailgate switch has stopped working and the radio had lost its stations the last time she drove it, which was last saturday.

Reply | Report as offensive | Link