Excessive Parasitic Battery Drain

[chuck d.]

I am trying to fix my elderly dad's 99 Suburban 1500 SLT. Even with a new battery -after the thing sits for several days, it no longer is able to operate the starting motor. I inserted an accurate ammeter in series with the negative battery lead and something is drawing around 900 milliamps ( 0.9 amps) while it is parked. Now that I have found all of the fuses --I've removed each fuse and watched the ammeter. None of the fuses on the panel at the end of the dashboard changed the current draw as I removed them. The only fuse in the flat box in the engine compartment by the master cylinder that caused the amperage draw to disappear was the 50 amp one marked 'Bat'. What is this fuse supplying power to ?

Can anyone suggest how I can see an electrical schematic without buying an Owners Manual ? I will appreciate any suggestions.

 

[dwilson]

easy cheesey diagnostics

Start by unhooking one battery cable at the battery.

Take a test light, place one end on the battery post, the other on the disconnected cable.

IF IT LIGHTS UP, PULL ONE FUSE AT A TIME UNTILL THE LIGHT GOES.
CONGRATULATIONS, THAT CIRCUIT HAS THE PARASITIC DRAIN.

HERES WHERE YOU GOTTA GET DIRTY
Now, unplug each item on that circuit, one at a time, till the light goes out. (Put fuse back in first)

The item that kills the light, is your drain.

Hope this helps.