Something is Drawing Power When the Car is Off

[BBShark]

I have a blade style battery cutoff switch (like the electric chair) on the negative terminal. With the car off, ignition switch off and battery cutoff, I am reading .15-.25 volts. When I look at the current between the chassis ground and the negative terminal, I see 0ma.

Does this make sense?

 

[phantomjock]

Sounds like you have a Ground Loop.
Something is finding a path to ground - other than the primary. I bet if you cut the + with the blade it will go to Zero.
A hot-wired safety switch (roll-over fuel cut-off). or security system , maybe. Time to start pulling fuses and chase electrons.
Best of luck.

Cheers - Jim

 

[BBShark]

This is weird. If i leave the cutoff switch on and leave the car sitting for a day (possibly way less time) and open the switch (negative disconnected), then open a door, the footwell courtesy light flashes and then goes to a state where it is on but very dim. The footwell lights are LEDs.

Now I'm thinking that there is some capacitance in the system somewhere that charges up and discharges when the door is open?

EDIT: I just tested this theory. opened the door, lights flash and immediately dim. Voltage between chassis ground and pos terminal 3.30v. Left the door open for 10 minutes, voltage .50v. Another 10min, voltage is .26v. 10 more, .14v

 

[rtj]

I’ve had some of those cut off switches go bad. Especially the one’s mounted to the battery post. Also, always wire to the positive post.

 

[BBShark]

I think this is normal somehow. components that are in standby mode (radio, amp, EFI, etc.) are discharging when power is cut. So, when I open the door, the footwell courtesy lights flash.

The reason I say this is that battery voltage has been 12.46v for the past week and the parasitic drain is 1.50ma. I am going to try this again tomorrow after 24 hours of the battery connected and see if it is actually a drain or not.

 

[BBShark]

Tested with the battery connected overnight. 12.46v to start, 12.46v this morning. Parasitic drain this morning was 1.50ma. Anything less than 40-50ma is supposed to be good. I guess I will assume everything is OK.

 

[phantomjock]

and the diagonsis (root cause) for the previous condition?
What is the age of the battery? Just guessing at this end.
Congradulations if its solved! Keep a Jump Pack in reserve!

Cheers - Jim

 

[BBShark]

I think the root cause was standby power to any accessory (stereo, amp, EFI) that has a power supply. So, it is actually feeding stored power back into the system when the chassis ground was disconnected. At least that's my theory. I was kind of alerted to this by the flashing LED courtesy lights when you opened a door with the battery disconnected. If you replace the LED's with regular bulbs, there is not enough power in the system to flash them and the resistance is high enough that there is an immediate discharge.