Quantum Physics- or Where Are My Electrons Going?

[Bluebottle]

I've got a problem with vanishing electricity.
Our Quantum H4i is based around the components of a 1985 Fiesta XR2i with a 1800cc Zetec engine and all the associated electrickery including an imobilizer, probably a Ford unit.
The electriciy keeps falling out somewhere, not sure where. The car shows signs of a flat battery (dim lights, slow operation of central locking, not starting...) but the battery shows a full charge when hooked up to a charger. The battery has a little indicator window which shows green when ok, black for charge needed and red for cream-crackered. It's showing green, do I trust it or are they known to be decietful little devices?
The battery shows a good voltage, I've not yet done a current test (although the charger didn't show anything...)
This is the first time I've had to deal with a car with modern electronics and I'm way out of my depth here, any thoughts would be most welcome!

[Spudgun]

I'm no mechanic (but my father is) but I've heard him talk about something like this before.

It sounds like a bad earth somewhere and the body of the car is being incorporated into the circuit. Physics hat on: (something I know!) All that extra metal would create the resistance required to lower the current and produce the symptoms you describe.

I could be barking completely up the wrong tree, but after reading your post something 'clicked' in my head.

[Bluebottle]

Hmmmn, could be something like that, I need to get an ammeter onto it....
It's a fiberglass body, but there's still a lot of metal in there.

[Spudgun]

That would rule out the body then!! But the chassis could be involved..

[Bluebottle]

Forgot to say in my first post that the car can be jump-started with no problem.

[SL]

Agree with Spud, sounds like something is earthing and draining the current.

If it is just on starting then it could be ignition/engine earth or perhaps the alarm.

Sounds like another dirty weekend coming up

[Bluebottle]

I fear it may be the black magic box that is the imobilizer. Apparantly the Ford units are prone to dry joints. My multimeter dosn't show any current drain, but I don't trust it!

[kbam]

If the battery is showing a good charge, check your terminals, make sure they are clean and tight, and also any leads from the battery.
BTW, the car body, or chassis provides very little resistance, the more metal the better for current flow.

[Maisie]

We had a problem on Mr Frosty where the electric radio aerial was knackered and the motor was permanently trying to retract it. That caused quite a big current draw, and shortly after we ended up replacing the alternator, although that may or may not have been related.

[KC]

Depending on the type of alternator/generator used, the voltage regulator can cause a steady but slow drain as it fails that will drain the battery slowly. It also causes the charging power to appear good on gauges but is actually lower than recommended to run a car and recharge the system.

[avsfan733]

earthing is the same as grounding right? ...please excuse my lack of knowledge of decent english

[Dave Brand]

It's difficult to diagnose at a distance, but, although the battery appears OK, it's worth eliminating it before getting into a lot of work. Does the car start if you substitute another battery, rather than just jump starting it? I assume that, with just the battery on the car, the cranking speed is low?

A quick way to check for an earthing fault is to connect a jump lead between the battery negative terminal & some point on the engine (make sure you clamp on to clean, bare metal). If the engine now cranks at normal speed, you've got a high resistance somewhere, probably a corroded earthing point.

Spudgun, steel is a good conductor; that's why in steel-bodied cars everything electrical is earthed to the body rather than using a separate return wire!

[noise boy 2]

I agree with all of the current speculation that you have a grounding problem. I would make sure that the battery has a good ground to the block an dthe chassis, and that the engine is also grounded with straps to the chassis. Also I am assuming that you have checked for current drain with a test light (insert between the ground wire and the ground terminal on the battery, with the ignition off, the light should be out on the test light, if it is on, start pulling fuses to find the drain) Robert

[Bluebottle]

Put a different battery in it today and it seems ok, exept for all the electronic stuff giving me a hard time- i guess I shouldn';t have left it disconnected for half an hour...
We'll know for sure if it behaves in the morning Meanwhile, I'm studying the wiring diagrams with a magnyfying glass and a really bright reading lamp!

Last lime I had a mystery current drain was in the Granada which has an ammeter on the dash. Turned out it was the boot light!