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Intermittent electrical drain


NICKNIRO
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My old established, very professional garage and I are having a nightmare trying to identify what is draining the battery after 24 -48 hours on my 2010 Jeep Grand Cherokee S. We have disconnected the radio/satnav assembly , the oil warming system, the tailgate, the door locking, a siren and after 8 weeks off the road are no further forward. There appears little information on the subject and no offer of any dialogue from a West Sussex agent. Does anyone know where the second alarm sirens are on this model even. I surely can't be the only owner to have had this issue with a vehicle which has only done 72,000 miles. I'm based near Redhill in Surrey and would dearly like to hear from anyone who can help. Many thanks in anticipation. Nick Roberts

 

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Tracking down a parasitic loss can take time, especially on a modern car with lots of systems. I don't know if this is something applicable to your Grand Cherokee but a lot of modern cars keep their computers awake for up to 45 minutes after engine shutdown. The timeout varies by manufacturer and model but I have learned that when looking for a voltage drop you need to latch the door mechanisms with a screwdriver shank mimicking closing on the striker plate so the computer thinks the doors are closed. Likewise all of the courtesy light switches need to be jumpered. An oscilloscope may be necessary to monitor the car's systems to identify when they have shutdown. Only then can you go hunting for a parasitic loss.

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  • 2 weeks later...

Many thanks for your advice. I still have the vehicle off the road but they have found it has an alarm siren which has water damage caused by rain getting to it. Hard to believe but they think the management system is telling it to try to charge the batteries in the siren which are defunct. The next few days will tell.

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I have now had the Jeep back for a week and its starting OK even after being left for 72 hours. The problem was the alarm siren and batteries had been contaminated by water ingress and had burned the element out. The Management system was telling the battery to charge the alarm siren batteries all the time and they couldn't take the charge.

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BLUE STAR

Yep useful one to store in the memory cells.

Electronic management systems how did we manage in the past without them 🤔

Wonder how all the electronic stuff on the  hybrids will be lasting when they start to age, bet they'll cost a fortune to keep going, if parts are still available.

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