Hi,

I finally put an instrument grade ampmeter on my DB9 and measured the parasitic power drain. I had been using one of my handhelds and the car would draw 2 Amps and almost immediately drop to .5A, and then go down to .02A at which point my meter would shutoff due to lack of use. I figured that .02A was well below what would be needed to drain a battery. I finally bothered to put one of my 6 digit / rack mount DMMs in series with the battery. It followed the same pattern but about 30 minutes in it jumped back up to .5Amps. No amount of locking doors/unlocking doors would make a difference.

I'm led to believe that US cars don't have the tracker that our UK colleagues point to as the key current drain culprit. Does anyone have any other suggestions beyond just pulling fuses? I am going to put it back on the lift at some point and start doing that but wanted to solicit advice before beginning.

And, as an aside, it was a gorgeous day here in the DMV to take the Volante on the road. Best car in the world to go buy groceries in!

 

Car alarm? Do you check amp draw if it's locked or unlocked?

 

Locked or unlocked made no difference...

Thanks,
Larry

 

Really , the best way is to start pulling fuses or unplugging modules. Even cars over 10 years old have lots of modules that could cause a parasitic drain... Perhaps check Pistonheads as well.It could be as innocuous as a module not going to sleep. Most frustrating, good luck

 

thanks - fully prepared to pull fuses but thought I would ask in advance! I'll report back what I discover.

 

i'm probably way off base, but rather than pulling fuses, i would think it should be possible to use the probes on a multimeter to check whether or not a fuse is in the process of conducting current. should save some time, if possible.

 

Thanks for the thought. I own a set of probes, but unfortunately, for these types of situations the current is measured in series with the circuit and not in parallel (like voltage). Thus to know how much current is flowing one needs to put the ampmeter in the circuit (in series).

 

Another tool to consider when going after parasitic draws is a thermal imaging camera. You can get these a lot cheaper now, some even connect to your phone and use the phone screen. You view the various fuse boxes and notice a slight temperature change in the circuit causing the draw. Warmer fuse is the circuit drawing power. I've not tried it yet, but I have a thermal camera and plan to try this the next time I'm chasing sleep currents.

 

this is a great suggestion.

 

I own one... Given the ohmic loss across a fuse is close to zero I don't think I'll see it there, but the 6 W drain is somewhere in the car and measuring the boxes isn't a bad idea!

 

I don't know how reliable it is but I did come across the voltage drop method a few years ago:

 

OK, that is actually impressive! Here's a link to the power probe chart: https://m.roadkillcustoms.com/wp-con...op%20Chart.pdf