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Battery Draining

Stan Barnes

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I have a 1998 Avensis 1.8i Hatch Back. The Battery is almost new but something is draining the Battery when it is stood for a few days. If I disconnect the neutral terminal from the Battery and link in a LED lamp it glows with everything turned off. Any ideas please.

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Hi Oliver, it sounds like you have whats called a parasitic drain.

You need to Isolate the drain, use the LED as a current detector to confirm a current drain. With the car off and all accessories turned off, remove one fuse at a time from the fuse box. If the LED goes out after removing a particular fuse, the circuit controlled by that fuse is causing the drain. Refer to your owner's manual to identify whats connected on that circuit.These are the common current drain reported in a 1998 Avensis.

Interior courtesy light or boot light, Faulty door switches or the lights themselves can stay on and drain the Battery. Check if any lights are staying on unintentionally, especially the courtesy lights that illuminate upon opening a door.

Aftermarket electronics,similar to before, aftermarket installations like stereos, alarms, or phone chargers can cause parasitic drain. Try disconnecting them temporarily to see if the drain stops.

Boot release mechanism, A malfunctioning boot release mechanism can sometimes cause a drain.

Central locking system, the central locking system, especially if malfunctioning, can drain the Battery on some vehicles.

Faulty diode in the alternator, as I mentioned earlier, a faulty diode in the alternator can allow current to flow back into the Battery even when the car is off. Once you have isolated the circuit causing the drain, you can look for the issue with that component on that circuit. This might involve checking the wiring harness for shorts or replacing the faulty component.If you're not comfortable with electrical troubleshooting, it's best to consult a qualified mechanic to diagnose the current drain.You can buy a multimeter to measure the current draw more precisely than an LED. Hope this helps.:smile:

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16 hours ago, Stan Barnes said:

I have a 1998 Avensis 1.8i Hatch Back. The battery is almost new but something is draining the battery when it is stood for a few days. If I disconnect the neutral terminal from the battery and link in a LED lamp it glows with everything turned off. Any ideas please.

Hi, as Bper states above, you need to isolate the drain. By sheer coincidence, my fathers Ford Fusion recently had a parasitic drain, which was leaving the Battery flat overnight. The sequence I checked was as above, check courtesy light, boot light, glovebox light (if present). Then check for anything 'aftermarket' fitted like a stereo, alarm, Dashcam. Those are very likely culprits. Again, as Bper states above, you can use a multi meter (which is what I did) in the following way.

I did what I should have done at the start and rigged my multi-meter up to look for fine margins (please see pictures). I noticed straight away that there was nearly an amp draining with nothing on (0.78a). I am no auto electrician, but around 0.10 to 0.20a I would expect? Took fuses out one by one and the amp big drop was the radio (after factoring in the memory, so did it a few times). With that fuse out, reading went down to a more normal 0.06a. Since this discovery I have now read loads of articles online about the 6000CD (and similar) Ford radios draining batteries through a progressive internal fault (linked to the muting system apparently).

So my advice, to avoid the delays I had is identify the precise source first.  If anyone is interested in how I rigged my multi meter up, as long as you have a fairly decent one (mine's a Draper one, about £40-50) and some crocodile clips 2 of which have a 12v wire in between, take the Red lead out of its normal socket on the multi-meter and pop it into the 10a DC socket. Turn the multi meter dial to  the 10a setting. Undo you negative terminal clamp and take it off the battery. Attach one of the croc clips to the battery clamp (disconnected from the battery) with the other croc clip (with the wire in between) attach to the Red MM lead exposed end. Put the exposed part of the black lead of the MM to the negative battery terminal (use a spare croc clip) and this will then run through your MM what is going into your car from your Battery. You can play around then removing fuses and relays one by one until you get a drop in the readings on the MM. That's likely then to be your issue. It was with me.  


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