Fan noise when pulling away

[KJHXXX]

Hi all,

I have a 2016 94Ah REX (UK Spec) and I've recently noticed that when pulling away and getting to approx 10mph a relay clicks in the dash and a fan noise starts in the back somewhere. It sounds like (and could be) the REX cooling fan starts to run and then switches off if the speed drops again or after some time - bit tricky to tell.

I've never noticed this before and its annoying. There is no petrol in car so I know it's not the REX starting and I've tried switching off the AC / heating to eliminate this as well.

Any ideas?

Thanks.

 

[user 3172]

I’ve recently noticed this too. The symptom is very similar to your description but if I keep the stereo off, I notice it at other times too.

A definite relay switch from around the glovebox area switching something that makes a kind of quiet distant whirring sound from somewhere in the rear floor. It seems to switch on and off within maybe 5-10 secs in mine.

It’s not rex and it’s not cabin ventilation as far as I can tell. I did wonder about the pump to circulate coolant / heating through battery ???

Any ideas anyone?

Funny thing is, I can’t recall hearing it from new but I generally drive with music playing.

 

[jadnashuanh]

Could it be the pump pressurizing the REx's gas tank? It wouldn't need to run very long, but if your tank was essentially empty, the air in there will expand and contract more than just the gasoline, and could run longer. It would also be more prevalent when there's a big temperature change.

 

[KJHXXX]

Hi all. I'm starting to think that it is indeed the pump for the battery heating and cooling. Perhaps this is linked to the cold weather at the moment but I've never noticed this noise before. i might try and see which relay is clicking over and that should explain it!

 

[user 3172]

Could it be the pump pressurizing the REx's gas tank? It wouldn't need to run very long, but if your tank was essentially empty, the air in there will expand and contract more than just the gasoline, and could run longer. It would also be more prevalent when there's a big temperature change.

Don’t think so as on mine it’s off and on constantly. Plus my Rex is full so unlikely to take much work to do it. Without knowing the method behind this though, it’s difficult to say.

 

[RexMan]

Did anyone ever get to the bottom of the fan noise when pulling away ? my 2017 94 Ah Rex has been doing that recently.

 

[alohart]

It shouldn't have anything to do with battery pack heating because that's done with silent electric resistance elements. The battery pack is cooled with refrigerant that is circulated by the A/C compressor whose sounds are familiar to many i3 drivers. If the cabin heater is on, there is a pump that circulates the heat transfer liquid, but it should not turn on and off frequently.

I'm guessing that the sound being heard is the power brake vacuum pump which would run very briefly after using the brakes to stop (but what i3 driver does that? ). I heard this vacuum pump in our 2012 i-MiEV, but I can't recall ever hearing it in our 2014 i3 BEV.

 

[RexMan]

No it's definitely not the usual brake sound, it's coming from the rear left when at the rear of the car.

I've noticed it comes on at low speed and off if I stop and comes back when I reach a certain speed again, it was not there in the beginning only up until recently.

 

[DWGEC]

2019 BMW i3 REX 120 ah
Bought used a few months ago US central Florida and all seemed ok until a few weeks ago.
When I turn the car on, after a few seconds the cooling fan in the front of the car come on at high speed for about 5 to 8 seconds.
Seems to have something to do with temperature, in the morning it comes on but not at a high speed 72º+/-74º F.
In the afternoon it comes on at very high speed and makes a loud fan noise 92º +/- 95º F.
Don’t hear any relay click. The range extender cooling fan is in the back of the car and it’s not making the noise.
Dealer said “I don’t know, will have to look at another one and see if it does the same.”
Anyone know what temperature sensor (and where it is located) is that tells the cooling fan in the front of the car to come on and at what speed.
Anyone know the specifications for this temperature sensor?
Any ideas?
Thanks in advance.

 

[Phil0110]

I noticed too but I'm used to it.

 

[Pandersen]

I've recently gotten this exact same problem. When hitting 20-21 Km/h the fan starts for 8 secs and then stops again. Not that noisy but exactly as described by others. It runs again everytime I go from below 20 to above 20 Km/h - 7-8 seconds each time - and then stops again.

The weather here in Denmark is cold - 0-5 degrees C (30-40 F) and so this could be a factor.

I tried running the REX for 30 minutes on a drive, but this did not change anything.

Did anyone ever find a solution to this?

 

[Arm]

I suspect this is the cooling/heating system kicking in to condition the battery. Since the battery is cooled by the same system that also provides cabin heat/cooling, even when you have the fan inside the car off, you may still hear the system running because it's conditioning the HV battery.

 

[alohart]

I suspect this is the cooling/heating system kicking in to condition the battery. Since the battery is cooled by the same system that also provides cabin heat/cooling, even when you have the fan inside the car off, you may still hear the system running because it's conditioning the HV battery.

The BMW training manuals and TIS write that battery preconditioning in cold weather (heating) uses resistant heater wires below the battery cells (assuming that an i3 has the heated seat and battery pack option) whereas preconditioning in hot weather (cooling) is done with heat pump refrigerant. The heat pump diagram doesn't show a way for hot, compressed refrigerant to circulate through the battery pack, only cold refrigerant. This is especially true for REx models because they have no heat pump to provide heat to the cabin.

That said, a Norwegian i3 BEV owner swears that the battery pack is also warmed by refrigerant because the compressor runs while battery pack preconditioning is occurring. I have no experience with battery pack preconditioning.

 

[Arm]

I suspect this is the cooling/heating system kicking in to condition the battery. Since the battery is cooled by the same system that also provides cabin heat/cooling, even when you have the fan inside the car off, you may still hear the system running because it's conditioning the HV battery.

The BMW training manuals and TIS write that battery preconditioning in cold weather (heating) uses resistant heater wires below the battery cells (assuming that an i3 has the heated seat and battery pack option) whereas preconditioning in hot weather (cooling) is done with heat pump refrigerant. The heat pump diagram doesn't show a way for hot, compressed refrigerant to circulate through the battery pack, only cold refrigerant. This is especially true for REx models because they have no heat pump to provide heat to the cabin.

That said, a Norwegian i3 BEV owner swears that the battery pack is also warmed by refrigerant because the compressor runs while battery pack preconditioning is occurring. I have no experience with battery pack preconditioning.

I think the latter is true. Also, I've never heard of an i3 not having heated seats as an option.

 

[alohart]

I think the latter is true. Also, I've never heard of an i3 not having heated seats as an option.

On p. 84 of BMW's I01 High-Voltage Training Manual:

"The I01 is equipped as standard with a cooling system for the high-voltage battery. For this purpose it is incorporated in the refrigerant circuit of the heating and air-conditioning system, similar to current BMW active hybrid vehicles. If the customer orders optional equipment 494 (Seat heating) for driver and front passenger, his I01 also has heating for the high-voltage battery. The heat effect of the electrical current is used for heating up the high-voltage battery. This heating including the control is located inside the high-voltage battery unit. At a very low ambient temperature or cell temperature and with a connected charging cable, the heating is automatically activated if required in order to warm up the battery cells."

Living in Honolulu, I did not need heated seats or a battery pack heater and did not want to pay for option 494 when we purchased our 2014 BEV new. This option became standard in later U.S. i3's maybe as early as 2015. Enter the VIN of our 2014 i3, WBY1Z2C50EV285093, in your favorite BMW VIN decoder to verify that option 494 wasn't included in our i3.

 

[Arm]

I think the latter is true. Also, I've never heard of an i3 not having heated seats as an option.

On p. 84 of BMW's I01 High-Voltage Training Manual:

"The I01 is equipped as standard with a cooling system for the high-voltage battery. For this purpose it is incorporated in the refrigerant circuit of the heating and air-conditioning system, similar to current BMW active hybrid vehicles. If the customer orders optional equipment 494 (Seat heating) for driver and front passenger, his I01 also has heating for the high-voltage battery. The heat effect of the electrical current is used for heating up the high-voltage battery. This heating including the control is located inside the high-voltage battery unit. At a very low ambient temperature or cell temperature and with a connected charging cable, the heating is automatically activated if required in order to warm up the battery cells."

Living in Honolulu, I did not need heated seats or a battery pack heater and did not want to pay for option 494 when we purchased our 2014 BEV new. This option became standard in later U.S. i3's maybe as early as 2015. Enter the VIN of our 2014 i3, WBY1Z2C50EV285093, in your favorite BMW VIN decoder to verify that option 494 wasn't included in our i3.

Very interesting to know!

 

[Pandersen]

I managed to stop the car quickly, and run out in time to verify it is in fact the fan for the REX running. Runs for 8 seconds then stops. My problem seems to be unconnected to whether the inside fan is running or not.

It's still too cold here to test if outside temperature is causing the fan to run, but I will try to go to a local supermarket parking garage and leave it there for 6-12 hours - I would expect the temperature to be 10C (50F) at least there, and maybe this will change something. Will update when I know more.

Thanks for the replies and updates here.

 

[Pandersen]

As a follow up I can report that once the temperature reaches approx 8-9 degrees C (~45-50 F) the fan stops running. So for me, all summer there is nothing - fan only runs when the REX is in operation (or after operation). Now it is winter here again, and I'm back to the same pattern as last winter.