MK5 Jetta Radiator Fans - how to trigger?

Hasenwerk

Vendor , w/Business number
Joined
Nov 28, 2003
Location
Quesnel, BC
TDI
1982 Cabriolet (BEW|VNT17|Stage4), 1989 VW TriStar Syncro soon-to-be CR TDI (CBEA), 2001 Ford Ranger Edge 4x4 (ALH|VNT17|R520|Stage4)
I installed a 2009 Jetta MK5 (CBAA) radiator and intercooler in my 2001 ALH Ranger. The intercooler works fantastic and everything fits in my Ranger with minimal work.

The issue that I am having is what signal is needed to turn on the fans?

There is a four position plug - a heavy red and brown wire, which is 12V and GND respectively, and there are two light gauge wires BL/Y and something else as my color memory from yesterday is poor. I originally thought, seeing how they are 1mm wires, that they are a simple ground trigger for the MOSFET inside the two fans... however, grounding or putting 12V on these wires does not turn on the fan.

What signal is needed to turn the fans on? :confused:
 

Hasenwerk

Vendor , w/Business number
Joined
Nov 28, 2003
Location
Quesnel, BC
TDI
1982 Cabriolet (BEW|VNT17|Stage4), 1989 VW TriStar Syncro soon-to-be CR TDI (CBEA), 2001 Ford Ranger Edge 4x4 (ALH|VNT17|R520|Stage4)
Most fan controllers in VW/audi land use a PWM signal. My experience is with audi, and they operate as such...

Load reduction ignition power on one of the small leads, usually red with a tracer, and a PWM signal on the other. A PWM of at least 10% duty cycle must be present within about 10 seconds of applying power to the controller or the fans will default to full speed. The PWM carrier is around 25hz as I recall. The duty cycle varies from about 10% (fans stopped) to 90% (full speed).
Neat... MOSFETs, now the question is how easy would it be to bypass that and just use the MOSFET to be an 100% on - off switch...

MK4 and MK5 radiators behave the same ?
 

Hasenwerk

Vendor , w/Business number
Joined
Nov 28, 2003
Location
Quesnel, BC
TDI
1982 Cabriolet (BEW|VNT17|Stage4), 1989 VW TriStar Syncro soon-to-be CR TDI (CBEA), 2001 Ford Ranger Edge 4x4 (ALH|VNT17|R520|Stage4)

Hasenwerk

Vendor , w/Business number
Joined
Nov 28, 2003
Location
Quesnel, BC
TDI
1982 Cabriolet (BEW|VNT17|Stage4), 1989 VW TriStar Syncro soon-to-be CR TDI (CBEA), 2001 Ford Ranger Edge 4x4 (ALH|VNT17|R520|Stage4)
Just going to close the loop here and say that I have everything working.

There are 4 wires:
Heavy: 12V and GND > these go to the battery
Light: 12V switched and Speed via a 25Hz, 5% to 95% duty cycle change

If you want the fans to run without a controller it is possible. The 12V and GND are of course needed, if you apply 12V to the 12V switched wire (mine was BL/Y) for about 10 to 12 seconds and leave the remaining wire open, the fans will come on, and go from low to full in about 5 seconds more and stay at full.

A controller (simple microcontroller / Arduino) would be nice for different speeds, but if you just want to have a rad fan on for a hot engine in stop and go traffic or off-road situations, then "100%" will do just fine!
 
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