Let's be logical about this guys, I need some serious thinking here

Right, I am posting this from a very nice and posh hotell in Northern Finland with a nice and fast broadband connection for guests. I had a less than nice experience today, though, with my car. Having crossed the Baltic sea on a 70's style ferry taking 3.5 hours, I returned to my car, which so far had been fine, and the battery was dead. Completely flat; for those who have followed my tale this is the same thing that happened in York and on my drive, so this is the third time since mid-June that this has happened and indeed also the third time ever for me, I have now had the car for 12 months.

What happens is that the car, which now has a brand new Volvo battery and a brand new alternator and is charging fine, occasionally (and only occasionally) when left for 3.5 hours or more (this is the shortest period of time that I have left the car for and this has happened so it could be shorter but not longer), drains the battery completely. When I then leave the car the next time, nothing happens. So, we can rule out the old light-on-in-the-boot problem which drains the battery over night, every night. Something in my car is capable of sucking every last bit of power out of the battery in a very short period of time. But what? I have had the car in at a main and good Volvo dealer as well as at a good electrical repair shop. Of course, one problem is that mostly, the car is fine and so there is very little point in doing a fault check. I need some ideas, guys, on what to look for and what to replace. I want to find this problem and fix it. I like this car and intend to keep it.

George

[link:www.ttsservices.co.uk/my%20volvos.htm|http://www.ttsservices.co.uk/Signature.JPG]

'95 940 Polar LPT estate (B230FK/AW71)
'87 740 GLE Turbo Diesel Intercooler estate (D24TIC/ZF22)
'79 262C (B27E/BW55)

[migrator]

George,

Do you have full towing electrics fitted to this car? If so does this include a permanent live feed to the rear of the car? There is such a feed in the Volvo towing loom that I got some time ago. The advice given with the fitting instructions was to remove the in-line fuse from this supply whenever it was not to be in use. This supply cable is quite heavy duty by car electrics standards and if shorted in any way would be quite capable of carrying enough current to drain your system without causing the cable to overheat.

From what I recall, there is also a lot of 'extra' equipment added to your car. Knowing your normal approach I hesitate to suggest that there might be a wiring problem there.

[Peter Milnes]

George, our good buddy Padrig has been having very similar trouble with his 945 turbodiesel, the battery going flat overnight. He has not got a towbar yet so the wiring for this is obviously not in place. However I recently measured the current draw from the battery when stationary with everything switched off. There was 3 Amps current flowing! I chased this down to the alternator connection by removing the other wires on the battery terminal and measuring for current in the two wires which resulted in no current. There was still 3 Amps flowing with the connector in place on the terminal. I then removed the alternator connection from the back of the alternator and the current dissapeared. When reconnecting the alternator I noticed that the terminal was apparently making a pressure contact with the small terminal below the main connection. I routed the cable away from this connection and the current remained at zero. When he turned the ignition on all the lights in the instrument panel came on and the car started fine. He has not called out for my assistance since so I hope that it has cured his problem.

All the best, Peter

could it be something like the stereo, or an interior light thats not turning off every time?

if you call the aa out then they should be able to use a multimeter to source the fault for you

George,

In the 960 there is always power to the seat motors. I remember you mentioned having a problem with your power seat so what i'm wondering is if the seat could be draining the battery perhaps? A motor that was jammed would cause a serious current drain leading to a rapid loss of battery power. Normally the fuse would blow but, in the 960 at least, it has the self reseting trips so once they had cooled down it would supply power to the seat again. Likewise a window or the sunroof trying to close when it's already closed would do it and not necessarily cause any noise.

Graeme

Well, you all come up with good ideas but the problem is that the loss in intermittant. Neither the AA nor anybody else would be able to messure it. After the total battery loss on the ferry, I drove for five hours (i.e. battery then fully charged) and parked. By accident, three interior lights where left on for about five hours, and then I operated the central locking four or five times, watched a DVD in the car and used the seat and window. I got sitll start the car with no problem.

So you see why I am in trouble....


George

[link:www.ttsservices.co.uk/my%20volvos.htm|http://www.ttsservices.co.uk/Signature.JPG]

'95 940 Polar LPT estate (B230FK/AW71)
'87 740 GLE Turbo Diesel Intercooler estate (D24TIC/ZF22)
'79 262C (B27E/BW55)

[keith.talbot]

As you say - this is difficult as it is intermittant.

My only suggestion is probably not practical while you are on holiday (unless you have some keen electronics hobbyists you know nearby), but to put in a simple alarm to detect when the battery is being drained. When a current drain is indicated you can chase the "leak". Ideally this would be visible from outside the car, so you could stop, get out, lock, and see if anything is triggered then.

Current sensors would be ideal, but may not be trivial (either a big coil of wire wrapped around the battery earth lead, or maybe a hall effecct sensor).

You could maybe sense the battery voltage. In very round numbers a 70Ah battery drained in 3.5 hours is 20A from the battery - that would drop the terminal voltage significantly from it's 13.8 volts, IMHO.

This terminal voltage you would take to a comparator, wired up to a RED LED visible from outside the car, which would only illuminate when the battery was draining.

You could therefore check as you walked away from the car whether the LED was lit, and then go back and hunt the drain with your ammeter.

20 years ago I would have given you a circuit diagram for this - now I am out of touch with available chips.

oh - and current drain for this monitor could be insignificant (less than 10mA normal, 20mA when activated).

Maybe Maplin or someone sell a kit already to do this ?

Keith

http://pic7.picturetrail.com/VOL188/...8/23744414.jpg


Hi George,

The obvious temporary solution seems to be to disconnect the negative battery terminal when leaving the car unattended for very long.

(Hope you have the radio code with you)

The problem can be sorted out when you get home.

Colin.

1990 740SE B200E/M47, remote C/Locking.

Well it did not do it again and I am home now. What sort of applicance can do this sort of draining, so to speak? Could a little reading light do it or would it have to be larger items?

George

[link:www.ttsservices.co.uk/my%20volvos.htm|http://www.ttsservices.co.uk/Signature.JPG]

'95 940 Polar LPT estate (B230FK/AW71)
'87 740 GLE Turbo Diesel Intercooler estate (D24TIC/ZF22)
'79 262C (B27E/BW55)

[migrator]

George,

Something that Peter has put in another forum (760) may be worth considering. Could this be down to the old 'bio-degrading' wiring loom syndrome? If it is there could well be some points that are shorting out but not all the time.