Purpose of secondary battery wire (fusible link)

[Flash]

Just a general question about the 325e/i big battery cable's secondary wire with the inline fusible link and what its circuit controls.

Thanks!

[ChaseN]

A quick look at my ETM shows it powering the main relay, fuel pump relay, DME, and diagnostic connector.

HTH

[jlevie]

That is what that does. It's purpose is to provide full battery power to the engine management system when cranking the car. The starter load can result in a voltage drop across the primary cable and the separate wire for the engine management system avoids that drop.

[ChaseN]

That is what that does. It's purpose is to provide full battery power to the engine management system when cranking the car. The starter load can result in a voltage drop across the primary cable and the separate wire for the engine management system avoids that drop.

I knew it was there to power those components specifically, but didn't know it was because of that specific reason. Awesome info!

[engrlks]

I think I may have shorted out my system when my dist. rotor broke during a ride. Is it possible that this link broke (thinking that the car was in accident)?

If so, is it possible to test it without cutting of the shrink wrap?

[billybobjoseph]

If you have a good ohm meter with some backprobes, disconnect the battery ground then the positive cable. Use the backprobes to poke into the smaller cable on either side of the fusible link; infinite resistance shows the link to have been blown, low resistance shows the link is ok.

[matias88e30]

never seeing that in my 88is!