[S7eviev]

Hi all, here comes my first post .....
My 2017 Leaf ZE01 has what appears to be a problem with the engine cooling fan (started just after the seller's 3 month warranty ran out!). It intermittently comes roaring on when I turn the car on or even when I just plug in the charge cable. Not all of the time and sometimes it settles back down to a slow whine, or the fan speed hunts around for a while. If it starts roaring when I plug in the charge cable I can sometimes unplug the cable, put it back in, and the fan doesn't come on. It's all very confusing. The local garage thinks it might be the fan controller but are struggling to get a price and availability from Nissan (I can see them on eBay from the States for about £80). It is a Calsonic Kansei unit 21493-B210B. I'm also wondering if it could be the coolant temperature sensor (a lot cheaper) .....

I have a number of questions around how this all works. What does the fan controller actually do and how does it do it? What inputs is the controller getting? Is the coolant temperature sensor just a break/make temperature switch? If so, how does the fan controller decide what speed to spin the fan at?

If anyone could explain the whole setup it would be great and might point to what part is most likely at fault.
Many thanks

 

[S7eviev]

I haven't looked at the fan controller system in any detail but there will be two main inputs for it - one from the climate control system and one from the cooling system.

While the Leaf doesn't have battery cooling it still has a coolant loop which is pumped through the radiator, onboard charger, drive inverter and motor. If this coolant loop exceeded a certain temperature the pump would come on (probably intermittently) and at a higher temperature the fan would come on as well, mediated by road speed. (No need for the fan to come on if you're travelling sufficiently fast for normal airflow, so the fan should only come on at slow road speeds or while stationary)

The second input is the pressures/temperature in the high and low side of the heat pump system. Any time the car is stationary or moving slowly and the heat pump is enabled (either heat or A/C lights lit) the radiator fans will run at the low speed. When you go above a certain road speed it will switch off and if you're observant you'll hear it come back on again after a small delay when you stop the car.

If the pressures in the heat pump system are excessive - which can happen for example if the evaporator ices up (which I've had happen to me a couple of times in winter) the fan will go to the high speed, which is pretty noisy and easily heard.

One thing you could try while the car is turned on and the fan is going crazy is to turn the climate control completely off, (the small button below auto) this will normally turn the radiator fan off completely, or technically, remove any heat pump related fan control signal.

That would leave cooling loop temperature as the only reason for the fan to come on, so if the fan did remain on with the climate control completely turned off then either a sensor is telling the controller that the coolant is too hot, or the controller has a fault.

In the year I've had my Leaf I've never seen the cooling system heat up to the point where it calls for the fan to come on (with the climate control disabled) even though you can be sure that it has that capability.

Likewise while the system no doubt has the ability to turn the fans on during charging to help cool the onboard charger, I have never seen this happen and I suspect it would only happen in a very hot climate.

How technical/handy are you with diagnosing/fixing cars ? I do have PDF copies of the service manual for the Leaf and they go into great detail on the functioning of different components but it's pretty heavy reading unless you're into that sort of thing.

Thank you for your very detailed response Simon. It does sound very much like I do have a problem. My only vehicle maintenance experience is with old motorbikes! I'd like to look through the service manual - it would answer my question about how 'dumb' the temperature sensor is) - but I guess the problem will be testing the systems/components as I'm unlikely to have the necessary diagnostic equipment.

I think I have a couple of options: give it to a Nissan main agent and be prepared to possibly spend a whole lot of money; or ask my (very trustworthy) local garage to try changing the coolant temperature sensor (cheap-ish)- if that doesn't work maybe move on to changing the controller ..... In an ideal world I'd have a second Leaf to swap parts with!!
- Steve

 

[S7eviev]

If you look on the U.s version of the Nissan Leaf site I think I have seen this fault on there describing the same fault as you are having.
There is a temperature sensor that fails and I think it was an easy fix to replace and not too expensive sorry I have not got the link

Thanks for this, yes, I think it's the temperature sensor, when this fails the fan stays on. I wasn't sure if it was this at fault as the fan was not always on, and not always full speed. But it is now getting worse, I had to drive 25 miles along a motorway very late Saturday night, the fan was on when I started the journey, and was on when I arrived home. Not good. I'm thinking I should just replace the sensor anyway ....

 

[S7eviev]

Brilliant, thanks all. I'll let you know how I get on.

 

[S7eviev]

If you look on the U.s version of the Nissan Leaf site I think I have seen this fault on there describing the same fault as you are having.
There is a temperature sensor that fails and I think it was an easy fix to replace and not too expensive sorry I have not got the link

I replaced the coolant temperature sensor this afternoon and everything now all looks good! The fan (which had become always-on) is now silent.

To get to the sensor on my 2017 1st gen Leaf was really easy: remove the radiator top shield (take out 6 push-in plastic studs and then wiggle the tray out), then hold the windscreen washer fill tube out of the way after removing its one push-in stud. Getting the wiring plug off of the sensor was by squeezing the tab very hard and pulling. Remove the sensor body with a 19mm spanner (easy), wife puts her finger on the hole to stop too much coolant loss, move the rubber o-ring to the new sensor and screw the new sensor in. I've pushed the wiring plug back in to the new unit as best as I can but I'm not convinced that it is fully clipped in so will have to re-visit.

The new part was £9.90 from eBay (branded: 'Fuel Parts').

For interest I used my ohm meter to test the old and new sensor:
Old (broken) sensor: dipped in to cold water: 470 ohms; dipped in very hot water: 420 ohms. So very little difference.
New sensor: dipped in cold water: 2160 ohms; room temp: 2000 ohms; dipped in very hot water: 400 ohms. So a large difference.

So many thanks to all who have helped me with this.