Wiring 2 sources (engine and AC) to one cooling fan

[kabinet]

I'm trying to wire the AC to the engine cooling fan. Power from the engine is coming from ECM. It is fused and relayed. The power for the AC is coming from a relay grounded by a trinary switch. Here is a diagram of what I have going on. Can I just plug both wires into the fan or is that bad? If one system is powered and the electricity will flow back to the other system and that one also turns on will it do something crazy? I basically want to know if I can take the "?" from my diagram and connect it to the purple. Thank you!

[dhutton]

You can just connect both wires to the fan. I have done it that way no problem. Red ECM wire to purple wire.

Don

[kabinet]

Thanks, Don!

[CJD Automotive]

I would just connect the ECM feed to the 87A pole on the A/C relay.

[dhutton]

I think you get some redundancy and a slight improvement in reliability when you connect the relays in parallel as I suggested rather than connecting them in series.

Don