Self depleeting 12v

Hi
I have long driven with a malfunction heater. Getting it fixed in Norway has beed tricky to say the least. Lately the problems have escalated.

I have to following issues:

1. The 12v battery is depleting itself.
2. The key seems to work sometimes, but not allways. (I have changed the battery in the FOB)
3. Headlights will suddenly turn on by itself when I am parked.
4. Sounds from the front of the car by the passenger side front light when parked. It could be the pump for the windscreen washer fluid.
5. Sounds from the back door when parked. Repeating sound, maybe connected to the washer fluid or something else.

I bought a new 12v battery 2 months ago, but it keeps running low. I am unsure if it charges during driving, but I don't know how to check it. Lately the battery takes no charge, and I get a "P lock malfunction". That goes away when I install the battery from our other car.

Does anyone have any clue what could cause all these symptoms? Is it a faulty brain? Faulty DC-DC converter?

Any checks I can do myself and report back here?

Cheers!

Fairly typical from what I read that the heater and DC/DC converter often quit at the same time.
I recommend some type of small ( 2 amp to 10 amps rated) automatic battery charger should be put on the 12v battery every night until you get this sorted out.

You can check the voltage of the 12v system when the car is on. It should be 14v when charging. There's a thread around here that shows the fuse that blows in the DC-DC converter and how to get a replacement. An EV certified mechanic should be able to use those instructions to get it working if that's the problem.

Also, you can try to measure the current delivered by the 12V battery when the car is supposed to be completely off. Sometimes things fail and draw power when they shouldn't. If you can monitor the total 12V current, you can pull fuses one by one until the dark current drops to a reasonable value. Then you will know which devices to troubleshoot for failure.

You can buy a voltmeter like this

https://www.ebay.de/itm/Car-Vehicle-Voltmeter-Voltage-Gauge-Volt-Meter-Cigarette-Plug-Monitor-12V-24V-IP/291956203039?hash=item43f9f21e1f:g:1hUAAOSwcUBYO86a

to check the onbord voltage.

Did you check the DTC (Diagnostic Trouble Code)?

Kind regards from Austria

miimura said:

Also, you can try to measure the current delivered by the 12V battery when the car is supposed to be completely off. Sometimes things fail and draw power when they shouldn't. If you can monitor the total 12V current, you can pull fuses one by one until the dark current drops to a reasonable value. Then you will know which devices to troubleshoot for failure.

Click to expand...

Hi. What equipment is recomended to measure the current delivered? Do I have to use a voltmeter directly on the 12v battery?

Cheers!

Really need a clamp-on DC ammeter. Maybe $50(USD) for local hardware brand, quality would be Fluke but not needed. Must read DC, the cheap ones are just AC.
An electrician friend would have one for testing.

When my interface computer failed the battery was drained overnight with a 2 amp draw. Not sure that is your issue.
First do a simple voltage check with vehicle in Ready mode. Should see 13.5+ volts on the 12v battery to indicate charging.