This seems to be parasitic draw month and I came across this South Main Auto video on his approach. As you may know, Eric O of SMA is my favorite YT mechanic and I can’t say it any better than this. I especially like his trick of patching in an inexpensive standard ammeter using a make before break approach as he lifts the battery cable off the battery. Wonderfully simple, cheap meter, no extra gadget, does not wake up the computer. You can either do voltage drop testing across fuses or pull them in sequence to find the offending circuit. Parasitic draw below 120ma is considered the upper limit by most sources, under 50ma better and under 25ma is golden. Enjoy:


Edit:

I’ve never had to do a parasitic draw test on my blazer so I grabbed a meter to see how our trucks behave. The old trick of maintaining contact as you disconnect a positive cable from the battery is probably not necessary with a modern meter because I broke the connection and then inserted the amp meter which woke up the computer and drew about 2 A momentarily. Most modern meters are fused for 10 A so that shouldn’t be a problem. In less than a minute it had dropped through two stages first to about 800 mA and then to 65 mA. Three minutes later when everything went completely asleep the current draw was 5 mA.

George