So I have an 05 S4r. On the way home from work the other day it seemed to be running really hot(230 degrees). The fans weren't turning on so I figured then I had a bit of a problem. I got home and tested the fans and found that the left fan as toast. But I don't think that that is the end of it. I found that the first fan is supposed to turn on at like 211 degrees and the second at 213. So either way the one working fan shouldve turned on, yes? This would probably mean that the water temp sensor is bad, yes? How do I test it to see if it's bad? Any help would be awesome! Thanks!

     -Miles

Are you sure the fan is toast?  How did you test it?  The easiest way to test the sensor is with a factory scan tool or the aftermarket VDST software particularly since Ducati does not give a spec in the repair manual.  Short of that, the sensor is an NTC thermistor, meaning resistance goes down with an increase in temperature.  This means as the sensor is heated, if you check it with an ohmmeter, resistance should decrease.

I checked the fan with a 12 v battery. The right side worked fine but the left didn't respond. I just don't know what it is that tells the fans to turn on. I've glanced at the wiring diagram and the fans connect to the ecu, which means something's gotta be telling the ecu to turn the fan on, yes? But I can't find what that missing link is. The water temp sensor is the only thing I can think of that could be connected. I'm stumped. I'm not sure where to turn short of replacing parts, you know?


    -Miles

Both temp sensors on your motor are the same part.

One is wired to your gauge temp display, the other is used by the ECU.

You could compare their resistances at a couple of temperatures.
Or swap 'em, and see if the fans work.

IIRC, the temp sensor on the horizontal is hooked to the gauge, but not 100% sure on that.

Do you have a DP ECU?

There is also a fan relay under the tank by the battery support.  It is a standard four prong relay.  The white/green wire and the violet wires are the trigger wires.  To check the relay apply power and ground to the prongs that go into those terminals and   you should have continuity at the other two terminals, or, key on jump the non trigger terminals in the socket and the fans should come on.

Quote from: Speeddog on June 07, 2009, 10:41:43 PM


You could compare their resistances at a couple of temperatures.
Or swap 'em, and see if the fans work.

Do you have a DP ECU?

I just got done foolin' around with it some more. It is the stock ECU. So the Sensor that is connected to the gauge is fine because obviously the gauge tells me the engine temp. But you have a good idea there, i could swap them to see if they are bad. Still am kinda lost though, i feel like there is something i'm missing in the cooling system. The two water temp sensors, the thermostat, the radiator, and the water pump, yes? The troubleshooting continues...


   -Miles

Just checked the other temp sensor and it's good. On to the next idea...