ISOBUS disconnects when using in-cab

[Will Turner]

I've got a Fendt 724 with an agrispread lime spreader, all working fine, but I want to plug in a data logger to the 9 pin ISOBUS in-cab connector. However, even just plugging in the 9pin cable alone disconnects the spreader from ISOBUS and it refuses to reconnect, until I unplug the cable. Even plugging in a cable like this - https://agro-center.de/en/adapter-incab-agwxxx700532.html disconnects the spreader.


What am I getting wrong here...

 

[Wombat]

The 9 pin has a can loop in it that disconnects depending on the voltage on a pin to allow a longer cable loop to be installed via the 9 pin without compromising the isobus. So either the cable is triggering the disconnect relay without then having loops in it to join the bus back together

 

[Will Turner]

The 9 pin has a can loop in it that disconnects depending on the voltage on a pin to allow a longer cable loop to be installed via the 9 pin without compromising the isobus. So either the cable is triggering the disconnect relay without then having loops in it to join the bus back together

Thanks Wombat, this is my leading theory at the moment, I just don't see how a 30cm long cable could trip the NC relay! Time to build a cable and test.

 

[Will Turner]

I've found the problem - in the preassembled cable I was using Pins 1 and 7 were connected. Which means you can't treat it as a <1m stub cable, you have to forward the incoming CAN signals out of the cable again manually (which is the case if the cable were >1m anyway).

Thanks again for your help Wombat and pointing me in the direct of the NC relay.