Drained Battery.

Ok , I know this is an old issue and I have seen a number of posts on it but none of them tell me what I want to know. Last night the battery on my L322 completely drained. I have 2 suspects , one being the Sat Nav unit and the other is the Final Stage Resistor. Now I have temporarily changed the Sat Nav unit for a old unit I have with a bad Laser ( but at least the display works). However I wanted to check the following just in case it is a symptom of FSR failure. Ever since I have had the car ( over 2.5 years) , the blower always runs on for a couple of minutes after the ignition is turned off. As it did it from when I bought the car I did not consider it an issue. However I checked RAVE and cannot find this behaviour noted and therefore I am wondering whether in fact the FSR has always been suspect. Whatever took the battery out did it in about 12 hours and from a good state of charge to nothing at all.

Would be grateful for any information on the question above.

regards

The blower continuing to run once the ignition is off is NOT normal IMO, had my L322 over 3 years and mines never done that.
Points to the FSR to me.
HTH.

This may be an interesting read for you Sir

http://www.rswsolutions.com/index.p...343-mkiii-how-to-replace-final-stage-resistor

You can pull the HEVAC fuse and see if it still goes flat, can't remember which one, if you turn the blower off and it doesn't go flat that has also diagnosed it for some.
headlamp wipers not parking / defective can also do it

Bonnet switch can be another culprit. You can simply unplug it to check.

Heard of the diodes in alternator regulator pack going tits up and draining the battery in short order.

Not sure if the L322 needs to be locked or not for all ECU's to revert to standby, but:

• First buy something like this 20A Ammeter.
• Insert inline with battery +ve
• Disconnect bonnet switch so you can leave it open while testing
• Turn everything off
• Shuts the doors, and wait for it to fully go into standby mode.
• It should drop to less than 50mA

If not, you should be able to pull various fuses to see what's still draining the battery. Repeat the tests with the car locked & bonnet open.

Do NOT try to start the car, or you will probably blow the ammeter.

mine never goes to sleep unless i lock it via the key fob, would locking it with the Ammeter in place be a problem ?
If mine is left unlocked it flattens the battery quite quickly

Thanks everybody for the advice. After removing the MK3 sat nav the battery stayed OK for 24 hours so I think that the immediate drain problem is solved but since the opinion is that the HEVAC fans should not run on after the ignition is turned off , I will change the FSR anyway. At the moment trying to avoid disconnecting and reconnecting the battery to test with an ammeter as the BCU can be temperamental after disconnecting and reconnecting the battery ( past experience) . Having said that if I use another 12v battery to keep the power up whilst I wire the ammeter into the -ve side I should avoid this but that will have to keep for a day with better weather.

I will get the Mk4 Sat Nav fixed and change the FSR and see how it is after that.

Many thanks

Vince

holidaychicken said:

mine never goes to sleep unless i lock it via the key fob, would locking it with the Ammeter in place be a problem ?
If mine is left unlocked it flattens the battery quite quickly

Click to expand...

Yes you can lock L322 with ammeter connected, in fact most things can be checked, except starting the engine. This would require the starter circuit to bypass the ammeter.

When I did this on an L322 last year the bonnet switch was the problem, so once this was disconnected the car locked ok, and eventually went to sleep. The drops in current drain seemed to be a multi-stage process (4A, 2A, 500mA and eventually 40-50mA), so I guess it depends how long the various ECU's & SatNav take to sleep each. Maybe some of them are snoring and waking others up ??

Some of the systems take a while to shut down, there is a small fan on the HEVAC that continues for a while i think.
I don't get a current drain i don't think, if i leave mine for a couple of weeks it turns a bit slower and i get the HDC inactive when it cranks.
i may have a small drain somewhere so i bought a fuse buddy a while back but have had bigger fish to fry recently so have not tested it.

Thanks. Out of interest what does the bonnet switch do . Is it not just related to the alarm ?

regards

Bonnet switch should be open circuit when bonnet is closed. It has two functions:

1. Contacts close when bonnet opens, which is intended to trigger alarm when required.
2. Badly adjusted or dodgy switch triggers intermittently when bonnet is close causing random alarms & battery drain. This feature can also be triggered by wind when bonnet hinges are worn !!

Thanks,
The bonnet hinges are good and it looks like the switch is ok but for the sake of making things more simple I will disconnect the connector and tape it up off for safety / weather proofing. I don't think anyone will want anything that is under the bonnet anyway