1995 Ford car

[Fred Page]

This car immediately discharges every fully charged battery that's fitted, sometimes within the hour. Several qualified mechanics have looked at the problem but all have given up in that there's no apparent reason. Everything that uses current has been examined and one mechanic has suggested fitting a battery key (switch?).

Has anybody on this forum ever had this experience? I'm not sure what a battery key is or how much it would cost - and of course whether this idea would work.
Somebody please comment - usefully if possible.
Fred.

 

[miles_hot]

sounds like there is a problem in the loom rather than with any component - some sort of short or leak to earth on the car body. Maybe someone could look at all the places where wires pass through grommets for you as a starter (no guarantee it will be that easy to find but it's a start)

I am of course a mechanical and electrical numpty so take that into account I'd be worried about a car which appears to have some sort of short and fitting an isolator switch would not seem to be a cure for the problem which could cause additional issues I would have thought...

Miles

 

[barkwindjammer]

There aren't many 'mechanics' around these days unfortunately, they're now fitters-take broken bit off fit new bit, I'm astounded tho' not surprised that a 'mechanic' would even suggest fitting an 'isolator' switch to a car that had a fault like this, your car is at risk of fire :shock: if that amount of amps is leaking in a very short time, forget 'garages' take it to an auto-electrician

 

[Digit]

A key switch isolates the battery, but that is not exactly gonna solve the problem.
Do you have a meter and a wiring diagram?

Roy.

 

[studders]

Alternator Diodes?

I doubt it's a short in the wiring as you'd soon see smoke at that rate of discharge. Has to be a faulty component somewhere, and quite a hefty component too.

 

[MickCheese]

Is this any good to you?

http://assets.fluke.com/appnotes/automo ... atbook.pdf

You need to check for current leakage and then be systematic. Isolate each component and check then one by one.

Or

Take it to an auto electrician as already stated.

Mick

 

[Digit]

Alternator Diodes?

They'd be high on my list as well. Back in the days when the rectifier package was external to the alternator it was not uncommon for them to fail.
Easy test anyway, disconnect the alternator.

Roy.

 

[matt]

If you have time on your hands then you can pop every fuse out of the fusebox, connect the battery, and then a meter. Watch to see what the drain is, if any. If, after a period, you're happy that nothing is leaking away, then start to put the fuses in and further monitor after adding each one. In theory you should get to the point where popping a fuse in triggers a rush on the current and that gives you some clue to which circuit is at fault. If it were me then I'd take that fuse out and continue with the rest to ensure no other circuit is doing the same. Once you've limited the source of the problem to the components hanging off the fuse/s in question get to work checking each one. The only final thought to bear in mind is that some components are not fused off the main fuse box (the starter for one I think).

I'm not an auto electrician - the above is just what I'd do to try and find the problem. I used to know a trick with a bulb soldered to some long fly leads but cannot remember what it was (been a long time since I've worked on my own cars).

 

[Dibs-h]

This car immediately discharges every fully charged battery that's fitted, sometimes within the hour. Several qualified mechanics have looked at the problem but all have given up in that there's no apparent reason. Everything that uses current has been examined and one mechanic has suggested fitting a battery key (switch?).

Has anybody on this forum ever had this experience? I'm not sure what a battery key is or how much it would cost - and of course whether this idea would work.
Somebody please comment - usefully if possible.
Fred.

Fred

Having perhaps too much time with car looms and wiring diagrams - I'll give it a shot (apologies if it's sucking eggs).

- connections are either Live or Earthed. A Defective Earth would cause starting\running issues, not the kind you are experiencing.
- Lives are either switched (ignition switch) or permanent.

- Permanent Lives

• Alternator

• Starter

• Radio

• side lights & minor things.

- Ignition Lives

• starter

• fuel pump

• heater

• main beams, horns, etc.

Note the alternator isn't a drain on the battery, but a feed - but a defective alternator could be a drain. The starter isn't connected directly but switched by the ignition and a solenoid (switch) which switches the power into the starter and engages the teeth of the starter to the flywheel. The starter - battery to ignition switch, then to relay (to handle the large current), starter solenoid (& starter) then to ground.

The fuel pump - assuming it's EFI - will be powered in a similar fashion - i.e. a relay will control the fuel pump. Not EFI - then there won't be an electric fuel pump.

Switched Lives - these will come off a main relay and then a variety of fuses. Relay's are usually open, when the ignition is off, so if one fails - they fail in the off position. Rarely they can fail in the on position - which could cause the symptoms you are experiencing.

First disconnect the battery + lead, insert a multimeter in series (with the multimeter set to measure DC Amps) and make a note of the current draw. Then leave it disconnected.

Assuming your phone has a camera, take a picture or ten - (failing that make a diagram), pull all the fuses out, effectively breaking most of the ignition Live circuits. Remove all the Relays (note where they go) and then disconnect the alternator and the starter.

Reconnect the + lead back onto the battery, with the multimeter (measuring Amps) in series and recheck the current draw. With all connections severed - it's should be virtually zero. If it isn't report back!

Assuming it is zero - reconnect back in the following steps,

- Starter
- alternator
- Relays (largest 1st)
- fuses (largest 1st)

If the "defective" circuit is "added" back in the current draw should show on the meter - if you don't notice it when connecting the fuse\relay.

The only exceptions being the starter\alternator - for these disconnect the + lead on the battery 1st and then reconnect as each item is reconnected, to check the current draw. Don't do these with the battery fully connected - there's a lot of juice going thru those cables compared to all the others. :shock:

All the other circuits can be checked with the battery connected (multimeter in series). The moment the current draw increases you should have identified the circuit causing the drain. Then you can track it down from unscrewing the fuse panel and checking the cables behind it, and the one\s going to the fuse\relay in question.

Sorry - it there is no magical solution. It is a case of elimination and trial and error and potentially @rse in the seat, feet around a headrest and head under the dash! :wink: Been there done that.

HIH

Dibs