I've tried to describe this just in words far too often so it's about time I added some piccies and video.

 

To measure the overall parasitic current correctly on modern cars, you need to use a bit of stealth.  There are various reasons for this which I won't go into, but it entails setting things up so that you can have the car fully locked up, whilst still accessing the battery, and the car not getting awoken by any interruptions to the current supply.

 

Start by opening the bonnet. Then push the bonnet latch down (like it would be if you let the bonnet drop again). Use a screwdriver or similar:

 

Now the car won't think the bonnet is open even though it is.

 

Loosen the battery negative terminal so that it can be pulled off vertically very easily, but then leave it fully down/connected:

 

Now ensure all doors are closed, all keys are outside the cabin then lock the car, and leave it alone for at least 30 minutes.

 

Set your meter up ready to make a measurement. Dial set to a range like 200mA DC and the probes in the appropriate holes:

 

 

 

 

 

Now the bit that requires a little dexterity and care.  Remember the important thing here is not to interrupt the current flow, or the many control units will all wake up from their sleep state, and the reading will be useless.

 

Put the red meter probe onto the battery clamp and hold it firmly on there, with a grip that means you can also lift the clamp up with that hand; practice this if it isn't something you can easily do, or employ an assistant to add an extra hand.

 

Put the black meter probe vertically downwards onto the battery negative post, through the battery clamp, so that the clamp can be lifted up around the probe, without touching it, or losing contact between probe and battery post. 

 

Lift the battery clamp clear and read the meter.  Don't be surprised if the reading jumps about by a few milliamps (mA) this is likely to be the LED on the drivers door blinking to show the alarm is set.  Video showing this process below :

 

 

Note down the numbers, then do up the battery clamp again. Unlock and open the car, pull the bonnet release to re-open the latch, close the bonnet and you're all done.

 

if the reading is significantly higher than a few (2 or 3) tens of mA, try again but leave a longer time between locking the car and taking the reading.

 

 

 

 

 

 

Edited 4 July, 20214 yr by Wino

Didn't the bonnet being open stop the car locking and shutting down properly?

That's why you flick the bonnet latch over, so the car sees it as shut. 

On 04/07/2021 at 17:01, Pete_Ex-Wino said:

Then push the bonnet latch down (like it would be if you let the bonnet drop again). Use a screwdriver or similar:

Oops missedb this bit sorry