No power at battery junction box

[stuartjbecker]

My 89 325i died mid-drive home a few weeks ago. No symptoms, and then quit. In my series of troubleshooting tests, I have found that power to the ICV is only ~2V, and power on pin 30 at the fuel pump relay is only ~2V. Discovered that when attempting to jumper the fuel relay to make the pumps run. From my limited knowledge I believe these and the DME get their power from the junction block's small post. The trunk mounted battery has a large, fat wire running to the large post on the junction block and a smaller wire with an in-line fuse running to the smaller post on the junction block. Tested the in-line fuse and it is still good.

I discovered that when I remove the small wire from the junction block's post I have a reading of 10V at the wire; put it back on the post and it drops to ~2V. Is there something sapping the juice past the junction block?

Thank you all for your input!

[spdracrm3]

something is putting a load on the circuit and making the voltage drop , but its also telling you that you have a resistance problem in the circuit as it should not drop so low when loaded (your basically seeing a voltage drop test in action ) so now do a voltage drop test on the rest of the circuit back to the battery (the test is described in the first page of the factory ETM's ,download yours here http://www.wedophones.com/BMWManualsLead.htm )

i think you will find a bad connection or that fuse is failing (it can test good (ohm)till a load is put on it )

[stuartjbecker]

It was a bad connection. With the R speaker panel removed, behind and below the glovebox, i found the small wire's insulation eaten away and the copper corroded and barely hanging together. Somehow water must have gotten back there. Thanks for the help.

[spdracrm3]

nice job finding it , its amazing how you can get a correct voltage reading with 1 strand left ,this is why it can be so misleading and best to load test circuits to be sure of circuit integrity