2 speed contour fan wiring


Well-known member
I have done some research and this is confusing the hell out of me.

Anyone have a good wiring diagram for installing dual 2 speed electric fans?

Is there a single switch that will allow me to run both high and low speeds without using a toggle or one?

Is there a descent 2 speed controller out there that will last?

I have read mixed reviews on the ones I have found and would rather build my own than chance it.

Thanks for the help y'all.


Famous Member
FML. I had this all types out and somehow erased what I've written.

What you want is a dual thermoswitch. Easy junkyardable ones are from most BMWs from the '90s or a mid '80s VW Jetta or Golf or a '90s Audi with the inline five. IMHO, the BMW option is the easier one as the VAG options have a huge M22 thread. I guess either way you're welding a nut somewhere. :) You need either a pair of relays (one for each speed) or easier/cheaper is the fan relay from a '90s FWD Volvo. Check this:


You can also go aftermarket for the system - Hayden, Derale, and others all make 2-speed capable controllers, but you'll spend a fair amount of money. The upside is these kits use sensors/probes that are far easier to fit than the M14 (BMW) or M22 (VAG) sensors - typically 1/8" or 1/4" NPT. Also - IMHO - the aftermarket adjustable ones will let you run higher temperatures. The BMW switch is 180/195 (IIRC) which might be too low for an old iron engine. You'll probably be giving up some fuel economy and making some extra smog running that cold. You can get around that to some degree by creative location of the sensor (cold side of the radiator, etc.), but the adjustable ones do let you dial in the temp a lot more easily. Upside to the BMW/Volvo solution is that they're factory parts and will probably dramatically outlast anything aftermarket. I have a Derale adjustable controller in my XR4Ti and it's eaten two of them over the last eight years. I'm expecting the third one to die any minute now. :(


Well-known member
I found an easy wiring diagram for the Taurus 2 speed fan and plan on adjusting it for dual fans using the VW switch.
I will use a hose adaptor and tap it for the switch. I've found most put these near the top radiator. I'm not sure where the best place to put the switch is though.

Right now I am waiting on the diodes to show up so I can start the wiring.

This is the way I plan on wiring the fan up.


  • image.jpeg
    1.9 MB · Views: 33


Famous Member
Wow, that seems unnecessarily complex. You only need two SPDT relays, using three SPST relays is I guess a solution, but it seems pretty clumsy to me. Also, putting the diodes in the current path to the fans results in needing some serious diodes and possible loss in forward bias mode. Honestly, I would not pursue this. I would really recommend just finding a Volvo relay, either in a junkyard or off ebay for $20. Failing that, here is the simpler approach with two SPDT relays:


SPDT relays have two outputs, one that is always connected and one that is switched. In this configuration Relay 1's resting position goes nowhere (87a). When it's energized by the ignition switch being turned on AND the low temp switch triggered, it switches, connecting your battery to output 87b.

Relay 2's resting position is connected to the low speed fan. So, when Relay 1 is pulled down, Relay 2 immediately passes battery voltage to the low speed fan. When the hi temp switch is triggered, it switches Relay 2 and the high speed fan is energized.

It's a lot less complex and a lot less wiring. not to mention eliminating two giant diodes.

Note that this configuration does not account for AC as your diagram did. If you want the AC to turn the fan on, you would connect the AC switch to terminal 85 on Relay 1, same place as the ignition switch goes. You will want a diode on the AC switch leg to block voltage going directly from the ignition switch to the AC system, bypassing the AC switch. But this only need be a tiny diode to block a few mw of power.

Amazon has 5-packs of SPDT relays for $14, complete with connectors: https://www.amazon.com/Pack-EPAuto-Rela ... SPDT+relay

They are 30a rated, and should be enough to run the Contour fans.

Forgot: You are going to want to fuse this - I would recommend two fuses, one each at Relay 2 87a and 87b. But, you could also cheat and put one fuse between the battery and Relay 1 30. The two fuse scenario is preferable, placing the fuse as near the load as possible and might allow one speed of the fan to run even if the other fails. One fuse is one point of failure, and runs the risk of cooking the relays.

F-250 Restorer

Famous Member
I thought it best to dig up an old thread. I've been using the Contour dual fan set up for several years—switching directly to high speed. Now I want to two speeds. I don't want to use an aftermarket controller because failure will leave me stranded waiting for the postman to deliver a new controller. So, I was looking at, and have several, of the Volvo relay pack, triggered by a bmw two speed thermo switch.

But! what all the threads don't mention is that the Contour fans are single speed fans. Ford created two sp fans out of them by running the low speed through a resistor. The Volvo relay pack puts out low and high speeds, so the oe resistor is not needed. However, that would mean running two wires (low and high speed) to the one power wire on each fan. So, if the low speed power wire is hot, then you'd be sending power along the high speed wire back to the relay. The same for when the high speed wire is live. How do you prevent that feedback? Diode? Which one?