Hello all


What can cause the engine fan on a Puma TDCi engine to run almost continuously? It is behaving as if AC is on, so in "low speed" mode.


Main radiator and AC fan runs as soon as engine is started, and stops when engine is stopped.
Engine is cold, and sensors seem to be reading OK (CHT, IAT) - and all behave as normal.
Removing low speed fan relay, and the fans stop - but it appears the ECU is requesting the fan to be on as there is power on the "relay on" line once engine starts.
AC is turned off, and not in demist mode, and the switch to detect demist mode is okay. Compressor/clutch not clicking in.
Fan & resistor module should be okay as the fans run because they are told to run from the ECU/Relay
f-super reports AC as off.


What else can tell the fans to run?
Is there an AC switch/sensor somewhere that could tell the fans to run (even when off?)
Is it possible the ECU is getting wrong data from CHT to make fan run, yet still display correct values in f-super?
Short on the control wire to low-speed fan relay?


What else?


(This is on a Transit, not Mondeo, but it is the same engine/sensors, so I am keen to see what ideas you all have!)