Parasitic battery drain help

[sladey]

HI,

I’ve had a problem for some time now where after being left a long time my battery will drain down considerably - sometimes completely flat and sometimes pretty flat

Today I decided to sort it out once and for all.

I watched a YouTube video and then connected the multimeter to the negative side of the battery and measured the current with nothing on - this was showing 0.08 amps which I understand is acceptable in a modern car but too high in an older car.

I took out the fuses one by one and nothing made any difference to the drain. I then removed the various leads from the positive terminal one by one until I found the one linked to the drain.

After some investigative work I found it was a cable coming out of the TOAD immobiliser (which has been in there for 20 years) - under the passenger footwell there was a couple of inline fuses. If I removed one it dropped the drain down by 0.01 and if I remover the other it reduced it by 0.07 - so that was the culprit.

I then tried locking and unlocking the car with that fuse removed - no joy. The cable in question is linked to the central locking function - so without it connected I can’t lock or unlock the car (though I could use the key but don’t think that will disarm the sensors - not sure - would have to test that out).

I followed the cable through to the other end and it connects to one of the wires coming out of the ignition switch. I checked the wire to see if it was shorting out but it seems OK - I beefed up the solder on one connection but it made no difference.

Does anyone have any idea on why this is causing a drain and whether there is anything I can do about it? I don’t know how long the drain has been there - I don’t think it’s always been liked that - my feeling is that the running flat problem started in the last couple of years.

Thanks in advance for any help - not a big fan of electrics


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[sladey]

One other point that has occurred to me overnight - the problem cable connected into one of the thick cables going into the ignition switch.

There was another thin red cable coming out of that right by the connection - not very long (about 20cm) but it went nowhere. Without thinking (something I’m quite good at) I broke it off.

Could that have been connected to something that would have prevented the parasitic draw? I can pull the ignition wiring out again and look for likely suspects but if so does anyone have any idea what that might connect onto? An earth? Another (switched) power line?


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[Ian Comerford]

I can’t help with your main query but have had similar issues in mine and it was down to an Odyssey battery that wasn’t performing. Is your battery a standard one?

[PeterK]

Could the fault be in one of the c/l door solenoids ?

[sladey]

I can’t help with your main query but have had similar issues in mine and it was down to an Odyssey battery that wasn’t performing. Is your battery a standard one?

Yes it’s a hefty standard battery - I’ve experienced the same effect with this battery but also with an odyssey that I sometimes use

[sladey]

Could the fault be in one of the c/l door solenoids ?

That’s an interesting idea and makes a lot of sense - I could disconnect those and re-test

[impmad2000]

So 0.08A drain from a 140Ahr battery (?) 72 days.
0.08A is a high drain by totals standards but may not be too unreasonable in older electronics. If this is a new state, perhaps something in the unit has degraded and causing the problem. Capacitors are prone to ageing and could need replacing.
Options as I see it…1) repair the unit 2) replace the unit or 3) put it on a trickle charger
Chargers like the Ctek have quick connection/disconnect connectors so no faffing around with crock clips on the battery terminals and the risk of shorting things out .
Don’t forget, a lead acid battery doesn’t like to be left discharged.

[sladey]

Hmm, yes but I’m getting the same with two different batteries

[sladey]

Also thinking it through, I was able to remove the battery drain and reintroduce it by disconnecting and re-connecting 2 wires from the positive terminal - so if it was a battery fault that wouldn’t happen

[911hillclimber]

That TOAD is a very old design?
Maybe just fit a modern immobiliser that could consume less.

[Bruce M]

As above, possibly a tired capacitor inside the immobiliser, or an IC. Potentially repairable, but might be easier to replace.