I've had a parasitic drain for some time, you may remember my posts. I had to install a switch at the battery for when the truck sits. From what I heard and can tell, this is not good for my computers, modules and other settings every time I cut he power. I couldn't figure anything out with the test light so I went out and bought a meter. When I put the red probe on the is connected negative cable and the black robe on the post, I initially get a reading of 1.2 amps, then it slowly goes to 1.18, 1.17, 1.16, few more and then .237, which I think is a fairly normal reading. My question is, why is it trending down? From what I've seen and read with a pull of 1.2 amps, I'm suppose to begin pulling fuses until I see it go down. I rechecked it many times, making sure I was holding equal and consistent pressure and I get the same results. Any answers?

 

Connecting after a disconnect is powering up many systems.
In those system are capacitors and memory that take a charge and consume power.
For one system that does this is the air bag backup power.
It is a large value capacitor that takes an initial high charge current that tapers down when charging is complete.
The radio has memory that takes a very small amount, the PCM takes a starting charge for it's program and memory as well as some other modules.
The final design current depends on the vehicle equipage.
You would need to find out what the back ground current draw is after the ignition is shut off and all system go to their resting current after some time interval.
.237 amp or (237 milliamps) may or may not be within limits.
Normally a good battery fully charged from the last time the truck was used should still crank the motor over for starting more than a month later.
I don't know what has been done but the alternator has what is called a rectifier stack of diodes that converts the alternator AC to DC for system uses. If these diodes should develop leakage, they can drain the battery after shut down but give no indication of a problem when the motor is running.
Good luck..

 

I know the truck has to be in a resting state, I thought since I hadn't moved the truck in the garage or anything, I could go ahead and try the new meter. Anyways, I put a new battery in this week, because the charge light came on. Ended up having to pull the Alt, had it tested, it was bad and replaced that this week. I'm tempted to leave my switch in the on position and see if I still have the drain. From my initial readings you would think I did, but when it goes down, possibly not. Maybe it was the alt, the whole time?

 

The rule of thumb is .05 amps or less. You are way over that. You will need to trace where that is coming from. Could be a module, headunit, amp ect.... Do you have any aftermarket electrical items on your truck? When are you taking those measurements? You should have the key out of the ignition and let it sit for about 30 min so the modules have time to "go to sleep"