intermittent battery discharge problem

2001 Chevy Suburban, 1500, 4wd kills itself overnight, but not every night.

Mechaic has traced the issue to door locks that run and draw 7-8 amps at whim. We're keeping one fuse out now until I can fix the correct switch. Is there a simple test to find a specific value for the door lock switches? Short of disconnecting each switch and seeing which pull test doesn't kill the battery? That could take days while waiting to see what happens.

If you have a digital multimeter that can measure current in amps, you can disconnect the negative terminal and connect the red lead to the negative terminal & the black lead to the negative post of the battery. This will give you a live reading of how much current is being drawn, disconnect the individual circuits one by one to see which one has the excessive draw. Before starting you want to make sure all the lights, accessories, etc are off to keep the current to a minimum to reduce the risk of damaging the meter. Also close off the door switch of the door that will need to stay open during this test (as well as the hood switch if there is one). If you need an illustration, there's a very good video titled something like: Parasitic battery draw by ericthecarguy on YouTube.

Done.

Anybody with anything?

Nobody has an idea? No tests for the switches?

yellow_cake wrote: If you have a digital multimeter that can measure current in amps, you can disconnect the negative terminal and connect the red lead to the negative terminal & the black lead to the negative post of the battery. This will give you a live reading of how much current is being drawn, disconnect the individual circuits one by one to see which one has the excessive draw. Before starting you want to make sure all the lights, accessories, etc are off to keep the current to a minimum to reduce the risk of damaging the meter. Also close off the door switch of the door that will need to stay open during this test (as well as the hood switch if there is one). If you need an illustration, there's a very good video titled something like: Parasitic battery draw by ericthecarguy on YouTube.

 Other than this reply which itterated all the completed tests, nobody has indicated ever seeing this issue, or hearing of a teat for the switches. Can anybody give me a clue? Thanks in advance!

 Now I know how homeowners feel hoping I'll reply to their questions on other forums.

Which fuse is removed to reduce the current draw? Are the vehicle doors locked or unlocked after the battery drains? This will help determine whether the problem is the lock or the unlock circuitry. There are three door lock switches as well as control by the BCM. The switches are single pole three position center-off, wired in parallel. To test the switches will require disconnecting each switch and testing with a multimeter or continuity tester. A defective switch would show continuity between the common and a switched terminal while at rest. Schematics of the vehicle wiring would be helpful in identifying the proper terminals on the switches. A service manual or Autozone.com would be a possible source.

 I forget the fuse #. 4th. from the right. 50 amp, controls seats, mirrors, locks, alarm.

Doors locked.

"To test the switches will require disconnecting each switch and testing with a multimeter or continuity tester. A defective switch would show continuity between the common and a switched terminal while at rest." This is what I needed to know. And even then, it could be the BCM according to the Mech. I have the Hanes book, but it doesn't have any testing procedure once you've gotten deeper into isolating the problem.

"A defective switch would show continuity between the common and a switched terminal while at rest."  I can only hope, as they say. With the fuse in, it can sometimes go days without drawing juice. But, with the truck all locked up and at rst, there are only so many things that can run/operate without turning the ignition switch. I'll try these tests today.

 Thanks for the info. I'll update if I find it, or cry for more advice.

 Well, I pulled the three relays and they all checked 'good' on the OHM meter. I'll have to do a hot test on them next, unless somebody suggests something different.