Hey all, fixing up a 2000 Blazer for my dad and its got a nasty draw.
Whenever I pull the INT BAT fuse my test light pulses and there’s a knocking from the interior. Switches for the mirrors and seats are also a little finicky (thinking corrosion) but maybe they could be connected? Let me know your thoughts!

 

1. What do you mean by a nasty draw?
2. Where does your test light pulse?
3. With everything off what is your battery voltage at the terminals?
4. Same question when the truck is running?

George

 

By nasty draw I mean within 30 minutes of running it goes flat dead.

Test light pulses when hooked up from the negative cable to the post and the 50A Maxi fuse is pulled. (The attached video is of the pulsing and faint knocking)

The battery is brand new, so across the poles is 12.6 when charged (currently at work so I’ll update with the test light hooked up)

When running it’s at 14.6, charges great.

 

So the battery goes dead after 30 minutes of the truck running or 30 min after your turn the truck off? And dead means that it will no longer crank?

George

 

30 mins after the truck is shut off. Reading my multimeter (alternator disconnected and starter disconnected) I currently have a draw of 1.4-1.7A.
It cycles between the two.

When I pull the ground from the main fuse box (left side engine bay) my test light goes out, but after pulling every fuse and every relay with it connected, the light stays on.

While the test light is connected, the voltage at the battery cables is 4.07V or so, but the battery’s charge is still 10.98V when going from terminal to terminal

 

Dead does also mean it no longer cranks, yes.

 

To check parasitic draw you have to let the truck completely shut down which takes a couple of minutes. Take the key out of the ignition, close the doors, remove the positive battery cable and bridge the positive connection from cable to battery positive post with a fused 10 amp ammeter in series. Keep everything connected and see what the current (amperage ) draw is after 5 minutes. Do this with a fully charged battery, 12.6v at rest.

George

 

Yep, that’s what I’ve been doing just with an ammeter from the negative terminal to the cable. I’ll recharge the battery and give it a shot on the positive side and update my findings

 

You will likely get the same answer. Can you get the current to drop below 100ma by pulling fuses. Remeber that the truck needs to stay completely dormant for 5 min. If you briefly looses meter contact the ECM will wake up and cycle again.

George

 

How much current does the ECM draw when cycling (if you know off hand)?