Thread: Air Con fan on when maybe is shouldn't be.

The fan will run after the engine is turned off IF the temp is high enough, this is to counter heat soak in the system. Most vehicles with thermo fans do the same thing. My kwacka GTR does the same thing after a run, in fact manuals state that care must be taken as fan can start automatically. If it is stopping after a short time all is good, The timing for cut in is controled via the ECM and is related to ambient temp and system temp and vehicle speed. under 80kmh and temp at 28c or higher. the ambient air temp sensor is located in front of the radiators.
Chers Scott

If the fan is on when you switch the engine off it means that the coolant temp has reached 110*C(cos then it starts on ECM request to help cooling) and didnt drop below 105(when the fan whould stop)... so your engine is running between 110 and 120*C as the gauge stood at the middle... this fan has a double purpose, one for aircon and the second to help cooling... try to stop the viscous fan with a rolled newspaper with engine running when the radiator is hot, if you can that's the problem

Hi There,
Been out for a run this afternoon, everything as normal, temp gauge where it normally runs, get home pop the bonnet and I have temps around the top hose of between 86 to 88 degrees C. Fan was on. If the temp is around high 80's the fan shouldn't be on should it. If I was finding temps around the 100 degree C mark would expect to find the fan on. Newspaper trashed so the viscous fan is OK, should be, only replaced it last month. That was because I had a busted blade not because it wasn't working.

In another thread somewhere which I can find now someone was talking abut a faulty switch somewhere, can't find the thread and can't find the switch right now.........

Cheers Marty.

There is no switch as such, the fan is controled by the ECM and relates to the temp as it sees them. The ambient temp sensor is in front of the radiator, its the plug tht looks like its going nowhere, this is also what tells the HVAC readout what to display as outside temp. It is possible this is a bit sus, also your temp gauge sender could be sad and sending the wrong reading.
Cheers Scott

PS did you read sierrafery's post and attachment? It explains the temps

As shown in the attachment the fan kicks in on ECM request when the ECM gets a 110*C coolant temp input, the gauge goes up from the middle only at 120 so if you are certain that the real temperature of the coolant is normal it might be a high reading coolant temp sensor...it's screwed into the elbow on the engine where the top hose is connected, cheap enough to replace it if you dont have a tester to read the ECT input... this fan would not stay on based on aircon requests with ignition Off only on engine management command so the ambient temp sensor is not an issue IMO, you can switch off the aircon to rule it out but i'm sure that this issue is not aircon related

Hi There,
Yeap got Sierraferys post with the temps, very useful, I'll go searching for the external temp plug next. Where is the external temp displayed? I had a look around couldn't see it. Checking the handbook......yea I know......

Cheers Marty

You can see the external temp on the aircon display if you select EXT but dont bother with that cos it has nothing to do with the fan's operation WITH IGHITION OFF believe me, operation after you stopped the engine is only for engine cooling purposes based on ECT sensor input

The fan will run continuously if the coolant temp sensor is non-operational or after it was non-operational but prior to the ecm temp sensor fault is cleared.