2007 Avalanche Battery Draining

Blackbird307 · March 16, 2023

Hello all,

My friend has an 2007 avalanche where battery dies within a few days of sitting. Tested for current draw with a total of 130mA when vehicle is off, here is what I found.

Engine Compartment Fuse Box

20A Fuse - ICP - 100mA

Cabin Dash Mounted Fuse Box

15A Fuse - LT STOP TRN - 15mA

10A Fuse - DSM - 5mA

Unknown

10mA ???

I have no specifications on what normal not running current draw is for these circuits....

After looking at wiring diagrams I determined that ICP serves both the Body Control Module, and Instrument Cluster. I unplugged the instrument cluster main harness connect at back and current draw dropped 100mA. Is this in line with what's expected for current draw with the instrument cluster when the vehicle is off? It serves no purpose when the vehicle is off and shouldn't be drawing current.

The instrument cluster had the common odometer display issue. I disassembled the instrument cluster and noticed the commonly blown LL2705 mosfet. The circuit board was scorched, traces disintegrated and the good pads weren't even adhering to the board anymore making the repair very difficult. I replaced the mosfet last night and tested it and dash odometer display lights up again. Did not test current draw though. Could be blown mosfet have drew 100mA (short between source and gate maybe?) To me that makes no sense since that circuit on the board should be dead until the vehicle turns on.... Will see later today if the 100mA draw from cluster is gone. Thoughts anyone?

Thanks again,

Edited March 16, 2023 by Blackbird307

Formulabruce · March 16, 2023

The other cause I found is cold solder joints caused by a switch

To a steel based solder and corrosion Also the battery saver timer can short on the board around it.

There was a guy on ebay selling rebuilt units with better bulbs etc.

He will only take trades that have not been serviced.

Blackbird307 · March 16, 2023

Should the instrument cluster be drawing any current at all when vehicle is off? My meter has an accuracy 1mA. It seems 100mA draw is too round of a number to be parasitic in my mind.

Further, a current draw of that much should leave my battery dead after ~2.5 weeks, and not 4 days?

Blackbird307 · March 17, 2023

So new development today. The odometer display stopped working, mosfet started smoking again. Turned power off, removed burnt mosfet, re-installed gauge cluster. Everything still works except the odometer display (like usual). Noticed that since I removed the LL705 MOSFET my 100mA instrument cluster current draw went away. Makes since because of 100 ohm SMD resistor in line and would probably draw about 100mA if mosfet failed in a way that it was still conducting. So that solves that problem. It's the only thing that has changed since initial current measurement.

What is causing the MOSFETS in these clusters to fail? Are they under rated? Maybe something else on the board is drawing a crazy amount of current. Also, are there some circuit board schematics for these clusters? That way don't have to reverse engineer this and reinvent the wheel so to speak, save some time. Logically to me that mosfet probably powers the display segments and some sort of controller determines the individual segments on what gets turned on so to speak. So maybe it's the actual display.

At this point I almost feel like it would be easier just to buy a new working cluster and transfer the odometer reading.

Thanks again,

Edited March 17, 2023 by Blackbird307