'92 525 - main relay triggered by ground or 12v?

[Jon K]

The schematics look like its a ground trigger, but you never know. I want to trigger it with 12v (ignition switch) so I guess I'll re-pin the relay socket but is anyway certain how its triggered?

[Ross]

Yes, grounded by the DME. Take note that pins 30(load input) & 86(coil) are supplied by a common source which will need to be interupted for your purposes.

[Jon K]

Ross - not sure I understand what you mean

[Ross]

The wire to both those terminals is always hot. If you are going to use 12v to trigger the relay @ 86(start of winding on the relay)you need to disconnect the existing wire there which is hot AND connected to 30 on the contact side. The brown wire @85 is the trigger wire to the ECM, for your purposes cut it and run a wire from 85 to ground.
86 & 85 are always the winding terminals

[Jon K]

So Ross - move 85 to always ground (chassis), cut 86 and hook it to the ignition switch output and that'll trigger the relay with 12v output over 87 (left alone), 12v switch over 86, 12v constant over 30 (left alone), and constant ground over 85?

Sounds good! Also, will this keep the orientation of the diode correct? I want to be protected by any flyback or voltage spikes. (The relay has a diode inside it)