Bad Earth?

[simone]

Gents,

Your help would be greatly appreciated, I have recenty purchased a 1990 Brightwheel with a Granada 2.8i V6 and am experiencing daily flat battery problems.

Basicaly everytime I use the car the battery goes flat by the end of the day.

The battery is brand new & the alternator has checked out fine! I must point out that the engine gets very hot so the 2x Kenlow fans stay on for an awfull long time.

Is it a bad earth?
Can anyone tell me where to normaly find the point on the chasis that the earths go to cause it is not obvious?
Any other suggestions?

Thanks,
Simon

[mylesdw]

The earth back from the block to the battery must be OK or the starter would not work, this implies that the earth for the alternator is OK too. What about the sensor wire from the alternator? Does the ignition lamp appear to work normally? Have you got a ammeter or a voltmeter installed, and is so, what do they show?

[grahamf]

I've had this before on my Spit. Try this to trace the leak....

Remove all the fuses from the fuse box (not owning a Cobra (yet) I suspect there is one!)

Make sure you have an ammeter and connect it in series with the battery lead

ie. 0v--------i|----A----

Now replace the fuses one by one, taking a look at the meter reading after each one. As you replace a fuse the needle moves indicating current is being drawn, then thats the circuit you need to look more closely at.

Oh, pleeeease don't start the engine in this state as your meter will pop!!!!!

Graham

[mylesdw]

grahamf: from what simone says, it is when he USES the car that the battery ends up flat, not when he, say, leaves it overnight.

[grahamf]

whoops!

i missed that bit....

[Robin427]

Even brand new batteries can be faulty - try swapping it with the one from your tin-top.

[simone]

I have had the battery on charge, today it was perfectly charged 13amps, when I turned the car over it was spot on.

I had a 30 minute drive around this afternoon stopping just once for 5 minutes (starting the car again then not so perfect), drove back to the garage put the meter on the battery and I was reading 12 amps.

I have an ammeter fitted to the car, the needle does not move from "0" & the ignition lamp works ok I think.

What do you think?

Cheers,
Simon

[Andy302]

Simone,

Check the voltage at the battery terminals with the engine running, you are looking for around 13.5 to 14V depending upon ACG output. Next question have you got a one wire or multiwire ACG? If one wire (self exciting) it requires reving at startup to get the ACG to generate, check battery voltage after giving it some revs. If its not a one wire check the +ve battery voltage feed to the ACG is present otherwise you wont get excitation of the ACG field and hence no charge output.

(Sorry ACG = alternator):thumb:

HTH

[mylesdw]

Simone: The figures you quote, 12, 13 etc would they be volts rather than amps, I am guessing they are?

First the ammeter that you have fitted, if it is working and wired correctly it should behave as follows:
1. Without the engine running, turn on the headlights, the ammeter should show around 10 amps discharge. Switching ANY accessory on should move the needle slightly towards discharge.
2. After starting the engine, the ammeter should show a charge of 10-20 amps for a few minutes, and then fall back to zero.
3. With the engine running, switching any accessory on may make the needle flick but it should return immediatly to zero (or very slightly positive).

If the ammeter behaves as above, it is working OK and it will show a continuous discharge if indeed the charging system is not working. Try going out for a drive with fans and lights on, if the ammeter stays at zero, the system is working.

[TonyD]

Simone,

Sounds like your alternator is not charging. If the ignition warning light is playing up, or connected wrongly the alternator may not charge.

Cheers,

Tony