Battery going flat overnight

[Pitmatic]

OK my corolla goes flat overnight (not a great song)

Battery replaced

Alternator replaced

Multimeter shows Battery is being charged

so I disconnect Battery and leave car over night and then next day reconnect it and the car starts fine

so I connected a multimeter between battery and car to measure battery drain and recorded 200-250 milliamps

I have a sony car stereo that is faulty so removed it to eliminate it and no change

Next I started pulling fuses to see what made a difference

No change until I pulled the 20A fuse for the wipers and the drain dropped to 50milliamps

The wiper circuit...... but that's switched by the ignition key??

With the ignition off and the fuse pulled I am reading 3 volts on one side of the fuse is that normal

Anyone had this happen and if so what was the cause? any advice would be greatly received :)

Mark

 

 

 

 

[oldcodger]

Hi,

That sounds a tough one.

Assume you mean you measure around 14.2v across the Battery when the engine is doing around 2000 rpm and that you currently have the new Battery in there ?

When you say goes flat, is there any juice in there at all, will the head or side lights come on at all , or will the starter attempt to turn ?

Agree with your method of disconnecting the fuses in though not sure about that stray 3v you measure as the wiper circuit, there are so many electrical paths in there.

As for the 250ma drain, thats unlikely to be your problem, with a 60Amp hour Battery it would take up to 10 days to drain, so you must have a much heavier drain elsewhere.

If the battery was new/fully charged,  to go flat overnight you need an average drain of about   7.5Amps, which is massive and at nearly 100watts   I would expect to find something would be getting hot or smell of burning if the car was switched off.

I'm no electrical expert, but would suggest you check things like the radiator fan is not coming on by itself, perhaps the rear screen heater, the door lock/window winders or even things like the boot light is not left on /or faulty.

For that amount current drain  the thing that could drain a lot of current without being too obvious , would be the starter motor / solenoid, though be careful as its a powerful circuit to check and can give lethal burns.

[Pitmatic]

Hi

Thanks for the reply

OK with the new Battery in and the engine running roughly 14.5V is measured this will drop slightly after half an hour so assume the Battery is charged and the alternator is changing its output (that's a theory)

When I say flat the Battery slowly turns the engine over a few times and then stops and then makes a clicking noise which I assume is a relay or solenoid with not enough power flapping about but either way its not got enough juice to start the engine leaving the charger on the car for an hour or two gives enough juice to get going again

So I left wiper fuse out overnight with battery connected and the car started fine this car has not been mucked about with and there is no alarm

I noticed as well that if I twisted the heater fan control the voltage changed on the pulled wiper fuse (n the side away from the ignition switch) which frankly has started to give me a headache the more I try to understand it, I might just keep pulling the wiper fuse till next weekend and have a real go over it then to figure it out

 

 

 

[oldcodger]

Cannot explain the heater control affecting the wiper circuit measurements either, though as mentioned a 250ma drop should not drain a charged Battery overnight.

However you say " leaving the charger on the car for an hour or two gives enough juice to get going again "   would think if you batery is almost flat and you are using a typical home Battery changer, then most of that short charge  will be eaten up by the starter motor and it will need some long runs to charge it a lot more from the alternator.

Typically a home chagerer eg a "6amp2 one will need arond 12-24 hours to full charge and almost drained Battery.

So its thats what you have been doing then yes that 250ma overnight could flatten an almost empty battery .

From the 2002 model onward , seems the wiper fuse is 25A and feeds into the combination SW before going to the motor.- see picture

The Sw assembly diagram also shows the intermittent timer and wiper relay are in or around there, so could be anything in and around there ..

 

 

[Gerald Ash]

If the fuse is out then the side connected to the Battery will show a voltage when connected to earth (not really earth but negative through the bodywork) and should be 0volts on the other side of the fuse holder.

As to the voltage difference when you move the heater fan that, I suspect, is because the fan speed is changed via a rheostat. A device which lowers and increases the voltage to the fan motor. Test both sides of the fuse holder through earth. Should be 0 on one side. 12v on the other. There may be a short in either circuit. If the heater fan and wiper is on the same circuit on fuse box which is likely as both are high amp items. If not then there should be no effect on the wiper circuit when turning fan switch