Dual cooling fan controller schematic.

[Galane]

Here is a schematic for a dual temperature circuit for operating a pair of single speed fans with two speeds.

The sensor is a Ford ECT, the one with the round connector with one pointed side and two pins. It uses the same type of plug as the air temperature sensor in the intake manifold.

I'm building this to install on a 1998 Mercury Mountaineer using a Ford Contour dual fan. With this I'll be able to set the fans to come on low speed at the temperature I want, same for switching to high speed. That's the early Contour fan, not the two separate fans used in the later years.

Dual fan, dual speed Cooling Controller | Flickr - Photo Sharing!

I got the fan control idea from a Peugeot controller. It switches the fans between series and parallel connection for low and high speeds.

It's basically two circuits joined together at the transistor outputs to the relays. The relay section could be configured any which way for different fans or anything else needing two control inputs. The electronic section could be replaced by a pair of fixed temperature switches.

I got connectors from Pointe-Products.com Far less $$$ than anywhere else.

Sensor: FORD: 3U2Z-14S411-LVA, WPT-437, Item No: 91-6995-CP $6.32
Fans: FORD: 4U2Z-14S411-DA, 88861096, PT2161, WPT-822, Item No: 99-8128-CP $8.04 (Order two, one to a package though the image shows two connectors.)

Some places want anywhere from $20 to over $50 each for those connectors. I wasn't going to spend almost as much money on a single connector as the fans cost.

The best price I found for PCB mount relay sockets is Newark. Durakool - DZ85AB-5-PCB

I'm building it on some perfboard in a Radio Shack project box. (Bleeping Radio Shack no longer has boxes their unchanged for decades boards will actually fit into and match up with the mounting holes.)

If anyone wants to do up circuit boards for these, have fun, make money etc. build and sell your own controllers from this - doesn't bother me. (Though tossing a bare board my way would be appreciated.)