Thermo fan control problem

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Posts: 11
Joined: Fri Apr 23, 2021 10:06 am

Thermo fan control problem

Postby RLY240 » Thu Aug 19, 2021 8:55 pm

I'm having an odd problem with the control of the thermo fan.
If I set the trigger type as "coolant temperature" then it doesn't matter what I do with the other settings but the fan just stays on all the time.
I've tried two different sensors and calibrations, in both cases the CTS reads as expected.

But if I set a second coolant sensor (generic sensor 1) and set the trigger type to this sensor instead then it operates as you would expect.

So it looks like there is something weird with the "coolant temperature" sensor as a trigger type for this output.

Anyone else had this issue?
CTS trigger on.JPG
Thermo fan wiring
CTS config.JPG
Trigger type set as coolant temperature

Posts: 11
Joined: Fri Apr 23, 2021 10:06 am

Re: Thermo fan control problem

Postby RLY240 » Sat Aug 21, 2021 7:03 pm

Update - swapping the coolant sensors also changed the way the thermo fan works despite the fact they both read the same.

CTS was a Bosch combined temp and pressure sensor (3 wire for each) and the generic sensor was a 2 wire style.

So for some reason the thermo fan control isn’t happy when the CTS channel uses the 3 wire sensor but works fine with the 2 wire. I am therefore wondering what other ECU functions that use the CTS output might also be affected (correction factors etc).

In my case I’ve just swapped the CTS over to the 2 wire sensor and it seems to be fine now.
Anyone got a theory on why this might be the case?

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