2006 S40 1.8L Parasitic draw ~0.5A. Where to start looking?

Rossosaurus · Post by **Rossosaurus** » 01 Apr 2021, 11:29

EDIT: I confirmed that the alarm only goes off when connecting a battery if the car is locked so I'm putting that down to being an anti-theft thing. Now I've just got to identify the drain. I checked with a multimeter and the drain is about half an amp. I pulled out each fuse and relay individually while using a multimeter and none of them caused the current draw to drop. Any ideas on what else I could try?

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Post was originally titled: 2006 S40 1.8L Alarm goes off when I reconnect battery after it goes flat. Normal?

Hi all

Currently got a battery drain on my 1.8L S40 Mk2 which I've had for a while. The battery goes dead to the point I can't unlock the doors by the fob after ~3 days but it wasn't an issue before as I rarely used the car. It's recently become more regularly used and now I need to solve the drain but everytime I switch out the battery for a full one the alarm now goes off and I have to spam the unlock key while the car deafens me which isn't ideal. However I can't remember if the car used to do this or if this is another issue that's developed I need to be concerned of.

So if possible could someone confirm if this was always the case and I'm remembering wrong or if the car alarm isn't supposed to go off everytime I switch out the battery. My suspicions are that if the cars unlocked when the switch happens the alarm doesn't go off but if the car is locked the alarm goes off when it gets reconnected as a theft deterrent or something?

Thanks in advance

Post by **RickHaleParker** » 01 Apr 2021, 12:52

Keep the batteries on a charger for a couple of weeks. There is a chance they are both sulfated from not being used enough. Float mode on the charger will reverse the sulfation and increase the capacity of the batteries. Depending on now bad the sulfation is it can take weeks to reverse it.

Store unused batteries connected to a smart charger of a battery maintainer to keep them healthy.

Rossosaurus · Post by **Rossosaurus** » 02 Apr 2021, 11:26

RickHaleParker wrote: ↑01 Apr 2021, 12:52 Keep the batteries on a charger for a couple of weeks. There is a chance they are both sulfated from not being used enough. Float mode on the charger will reverse the sulfation and increase the capacity of the batteries. Depending on now bad the sulfation is it can take weeks to reverse it.

Store unused batteries connected to a smart charger of a battery maintainer to keep them healthy.

Thanks for getting back to me. I've just gone ahead and bought a new battery as the 2 I've been alternating out are both probably like you said, pretty heavily sulphated and they're both quite old so it's probably time for a new one anyway. I confirmed that the alarm only goes off when connecting a battery if the car is locked so I'm putting that down to being an anti-theft thing. Now I've just got to identify the drain. I checked with a multimeter and the drain is about half an amp. I pulled out each fuse and relay individually while using a multimeter and none of them caused the current draw to drop. Any ideas on what else I could try?

Post by **RickHaleParker** » 02 Apr 2021, 11:32

Rossosaurus wrote: ↑02 Apr 2021, 11:26 I pulled out each fuse and relay individually while using a multimeter and none of them caused the current draw to drop. Any ideas on what else I could try?

Did you go through both fuse panels? There are two.

Rossosaurus · Post by **Rossosaurus** » 02 Apr 2021, 11:40

RickHaleParker wrote: ↑02 Apr 2021, 11:32
Rossosaurus wrote: ↑02 Apr 2021, 11:26 I pulled out each fuse and relay individually while using a multimeter and none of them caused the current draw to drop. Any ideas on what else I could try?
Did you go through both fuse panels? There are two.

Bloody hell that was quick XD. Yeah went through both fuse boxes and have the bloody knuckles from scuffing my hands on metal pulling them out to show for it. Only ones I didn't try were the high amp fuses under a little cover in the bonnet fuse box. i figured the areas those fuses covered would probably show more issues if something was wrong there. Also they were bolted down and I was too lazy to go into the house to search for an 8mm socket. But seeing as none of the other fuses showed anything promising I shall go and check those fuses tomorrow. Thanks.

Post by **RickHaleParker** » 02 Apr 2021, 11:52

Rossosaurus wrote: ↑02 Apr 2021, 11:40 I shall go and check those fuses tomorrow. Thanks.

See attached file. Start at the battery and work your way down branch by branch.

Be sure to check PF1 & PF2. It could be leakage through the starter or alternator.

Rossosaurus · Post by **Rossosaurus** » 02 Apr 2021, 12:00

RickHaleParker wrote: ↑02 Apr 2021, 11:52
Rossosaurus wrote: ↑02 Apr 2021, 11:40 I shall go and check those fuses tomorrow. Thanks.
See attached file. Start at the battery and work your way down branch by branch.

Be sure to check PF1 & PF2. It could be leakage through the starter or alternator.

2021-04-02.png

Awesome. Thanks!

Post by **RickHaleParker** » 02 Apr 2021, 12:13

Rossosaurus wrote: ↑02 Apr 2021, 12:00 Awesome. Thanks!

If it is on PF1, most likely one of the diodes in the Alternator's bridge rectifier has a fused PN junction. Which would explain your battery health problem also.

David+Son · Post by **David+Son** » 29 Apr 2021, 14:26

I used this to find a drain on my 850.(glove box light sw. due to warped door)

Parasitic Current Draw (search and copy a good chart) 50 - 80 mA can be normal for newer cars, your 500 mA is not.
Everything off
Close all latches
Lock car, wait ! hr (things are still working)
Meter on mV scale, read across fuses.
Readings will jump and then settle to a correct reading

https://us.autologic.com/news/testing-p ... ltage-drop

https://www.autonerdz.com/yabbfiles/Att ... sfuses.pdf