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Originally Posted by porschett
We used to do it that way 40 years ago but used a simple test light. The old ways still work!
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I did some more reading, and then some more testing. Found tyhat actually the old way does not work. I actually found that I have asbsolutely no draw, but when I first used the test light method I thought I did.
The issue with the light is when you first connect one end of the test light to basttery post and other end to disconnected wire, the truck gets a connection to the ECU but the test light (or multimeter) does not have enough current so the ECU never gets past the delay and just keeps trying - thus the test light will remain on perm making it appear as a draw is happening. That is why the test light never went out even after I pulled ever fuse.
The proper method is to run a jumper wire (on aligator clips) when the battery post and the disconnected wire - this creates the connection allowing the ECU to activate and after 20 seconds shutdown. At this point you connect the test light (or multimeter) to the battery post too and the other end to the disconnected wire - now you disconnect the jumper. If the test light goes on you have draw, or if the muti reads more than .035ma you have draw. At this point you can open the door to test and you will see the test light (or multi) turn on and then off again in 20 seconds.
Anyway, this method showed that I actually have no draw at all (just like GM told me when they tested for draw when the truck was still under warranty).
The odd thing is my battery always slowly draw down and once weak the H2 alternator never gets it back up even on long highway trips? When the battery is weak I need to charge it with an external charger. When this is done, the battery is strong for 3 months but eventually starts to weaken and again the alternator never gets it back.
Could the issue be that I have a cheap Costco battery that is actually slightly less cold-cranking amps than the original? I've read that the factory battery was just on the border of being adequate - perhaps my 'smaller' battery is being used more than the alternator can feed it?
Thanks