Electrical Contour Fan Wiring Help

I know there are people here that have done this mod. Not me, but others.

I can't remember who has though, let's reach out to a couple that might know. @mikestang63 ? @Chuckman ?

Its not too difficult. In my set up I used a BMW three wire- two speed sensor and sensor connector. Ran a ground to the block for the sensor. Ran the two other wires to a low speed and high speed relays. The BMW fan switch uses ground so they trigger the relays through ground.

In my car I have it wired so that when I cut on my AC the drivers side fan comes on automatically. The high speed fan comes on when above 202 degrees. Without AC the drivers side fan comes on at about 180 degrees both fans at 202. A diode is used on a jumper from the high speed ground trigger to the ground trigger on the low relay. It allows current to only flow from the high to low and not low to high relay.

I tapped the thermostat housing to accept the BMW sensor. Used two 40 amp relays. The fans only have two wires each. One is grounded to the chassis ( radiator support ) the others run to high or the low relay. The power feed for the relays come from the battery through two 30amp fuses...one each line. 85 sensor ground feed, 86 battery power, 87 battery power, 30 to fan. Jumper from 85 on high relay to 1amp diode to low relay 85.

sorry as I've never used that fan controller, but if memory serves me right- if you run the wiring through the stock contour thermostatic controller in the bottom left of your diagram, it will run your fans on low speed. Have you tried bypassing that and wiring the fans directly to your Hayden controller?