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!)

 

If the engine has detected a major fault it will go in to limp mode and the fan can start running all the time. Is the temperature gauge on the dash working as normal?


Any fault codes stored? The select switch for interior fans can go wrong, turn the fan speed switch in the car to 0 and see if it goes off.

 

Thank you for your suggestions.


Engine is not in LHM state, but good idea. No DCT codes stored at all.


Temperature gauge working perfectly


Internal fan works perfectly on all settings (and off).


Also, AC works fine when turned on.


Drives fine, in fact, I only noticed it as when I parked up once I heard the fan and thought the AC was on when it wasn't. (The demist switch isn't on, so the AC isn't on automatically, an the AC low pressure switch disconnected does the same).


I'm going to pull all AC fuses and see if it stops (as any powered line requesting the fan will then become dead/unpowered).


I will also replace the CHT sensor as even though it appears to read correctly for gauge and f-super, you never know.


Can't figure out what else it could be getting the ECU to request fan?

 

Good quality steel liners fitted correctly are no issue, Westwood liners will be just fine, used them for years.

Should also be nowhere near a grand fitted either.

 

We've been getting free power off our post (on and off) for for nearly 9 years now, we don't leave it plugged in from the post 24/7, that's why when they changed the post after 4 years nothing could be traced back to us, we charge the battery bank through the night when the light comes on, then when it goes off in the morning we unplug and hide the cable in the bush that we planted at the base of the lamp. A full charge of the battery bank lasts 4 days.

 

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