Originally Posted by
fray-bentos-uk
Thanks for that big wasa, can't say I understand all of the wiring, like 3 fan relays, and what is an Engine Control Relay?
Engine control relay, the ignition switch doesn't power up the ecu. A relay does. The ecu lets the relay power it up if the alarm unit says it's ok. Ie anti hot wire.
You don't really need it.
Fan relays, on some models there is a two stage fan and an extra fan for the Ac. The ecu controlled the Ac.
If you use an external fan switch then you don't need the above either.
I havnt just pulled this of the net. I pulled a loom to bits and traced it all out. I've done all sorts from the basic 2.0 pre pats 1993 Mondeo to the 2004 a Focus St170 and now the Focus Rs. I also have the st220 to look at.