A fellow gearhead (ABben32) from V8Buick.com suggested you fellows might be able to help me out here...

I've got a couple of Volvo radiator cooling fans (apparently from '01-'03 Volvo S60), one of which is mounted in my '71 LeSabre 455. It works great and moves an amazing amount of air, but it's wired direct from a relay to the fan motor, and only runs on high (and draws a ton of current when running)

Myextra fans all have a metal box mounted on the shroud, and the wiring goes through it to the fan motor. From what I've gathered searching online, there is some sort of 2-speed control that may be possible.

Apparently the violet wire comes from the ECU and carries the control signal. Anybody know if it's a simple 12V relay signal, or some sort of 5V square-wave?

Here's a pic of what I've got - Anybody know how I can get some control of the fan speed? How does the controller work?

 

There would appear to be no relay involved. It looks as though the decision to run at whatever speed is made by the ECM.

Attached are the official Volvo wiring diagram and a non-official system wiring diagram. They are both for the 2001 model but I have checked 2002 and 2003 diagrams and they are the same.

7/8 is the AC pressure switch; 7/16 is the engine temp sensor; 4/71 the cooling fan control and 6/29 is the fan.

Hope this helps.

[IMG]local://upfiles/4491/9227BC747AD244D396EE3E52DED08A66.jpg[/IMG]

[IMG]local://upfiles/4491/23A966C2C8C744D0898C6668B87ACB4F.jpg[/IMG]

 

Thank You, Bill of Durham! I think I can show the official diagram to an electronics-minded friend, hopefully he can translate the symbols and tell me what's what. (I'm hoping it's something relatively simple)

Thanks again!

James of Texas

 

As best we can tell from the official diagram (cropped and labeled below), there's a resistor inside the controller 4/71, and the "Circled K" items are transistors, likely used for switching.

But my friend can't make out how it works, he says it showing the switching transistors wired incorrectly, and thinks it's more of a "Here Be Transistors" diagram.

Anybody got any ideas, or anybody willing to put a voltmeter or scope on their Volvo's violet fan wire and find out?