DS4 (2015) Ventilation fan not working

[GimmeHeadPeace]

Hi,

For the past couple of years I have had an intermittent fault with the fan in the air system.

Some times it would work, sometimes it wouldn't. Other times it would start to work whilst driving. But now it just refuses to work at all.
I believe the heat elements are working as the only way to fully demist the windscreen is to drive with the windows down allowing passive airflow to draw the heat upto the windscreen.

I have the 2015 DS4 with dual climate zones for driver/passenger. I have seen other posts on here asking for vin numbers of the car but I am unsure how to obscure it so that only moderators can see it.

Anyone any ideas what could be wrong and generally depending on possible solutions the associated cost (approx is ok) of these?

[Hell Razor5543]

Hi and to the forum.

The site has software set up so that if a VIN is correctly posted up it will automatically be obscured so only forum staff can read it. You may well have seen something like VF7**************[VIN obfuscated, can be read by forum staff]. This is the software doing its' job.

EDIT; This happened when I entered JUST the first three characters. All I typed in was the V, the F and the 7, and the software saw that as the beginning of a VIN, so kicked in.

[GimmeHeadPeace]

Hi and to the forum.

The site has software set up so that if a VIN is correctly posted up it will automatically be obscured so only forum staff can read it. You may well have seen something like VF7**************[VIN obfuscated, can be read by forum staff]**************[VIN obfuscated, can be read by forum staff]. This is the software doing its' job.

EDIT; This happened when I entered JUST the first three characters. All I typed in was the V, the F and the 7, and the software saw that as the beginning of a VIN, so kicked in.

Thanks VF7**************[VIN obfuscated, can be read by forum staff]

[GiveMeABreak]

There are numerous posts covering this topic on the Forum.

It will likely be one of several possibilities depending on exactly what the issue is and you will have to do some testing yourself to narrow down the possibilities.

1) The system has Air Distribution flaps which are electrically operated by reduction motors to direct the air flow to the desired location.
So with the car running, gradually and systematically change the air direction on both sides independently from floor, to fascia vents to windscreen and decide if the air flow is changing direction as directed (note there can be a slight delay as the motors react, so wait a while before checking.

2) Additionally, the system has reduction motors to mix the hot and cold air as required.
Here, you need to wait until the car is at temperature and test the hot and cold temperature from each side of the car, varying the temp from cold to hot and check to see of both sides are changing temperature (it may be easier to keep the air distribution vents set to fascia level for this test.

3) The Blower motor itself operates via a Blower Control Module, not directly. The blower control module contains several resistors to increase the fan motor speed according to the Climate Control ECU commands and is designed to slowly spin up the fan from standstill as the car engine warms up, so as not to blast passengers with cold air when the out side temperature is cold. This module can fail.

4) I addition to the above, and because of the way the power is gradually delivered to the blower motor itself, there can be occasions due to moisture in the blower motor fan bearings than can cause it to seize slightly. As a consequence the power delivered by the resistor is not always sufficient to get the motor going. Others have temporarily bypassed the blower control module temporarily to kick start and free the motor up.

See the thread here - it will be very much similar to your DS4:

viewtopic.php?p=673222#p673222

[GimmeHeadPeace]

There are numerous posts covering this topic on the Forum.

It will likely be one of several possibilities depending on exactly what the issue is and you will have to do some testing yourself to narrow down the possibilities.

1) The system has Air Distribution flaps which are electrically operated by reduction motors to direct the air flow to the desired location.
So with the car running, gradually and systematically change the air direction on both sides independently from floor, to fascia vents to windscreen and decide if the air flow is changing direction as directed (note there can be a slight delay as the motors react, so wait a while before checking.

2) Additionally, the system has reduction motors to mix the hot and cold air as required.
Here, you need to wait until the car is at temperature and test the hot and cold temperature from each side of the car, varying the temp from cold to hot and check to see of both sides are changing temperature (it may be easier to keep the air distribution vents set to fascia level for this test.

3) The Blower motor itself operates via a Blower Control Module, not directly. The blower control module contains several resistors to increase the fan motor speed according to the Climate Control ECU commands and is designed to slowly spin up the fan from standstill as the car engine warms up, so as not to blast passengers with cold air when the out side temperature is cold. This module can fail.

4) I addition to the above, and because of the way the power is gradually delivered to the blower motor itself, there can be occasions due to moisture in the blower motor fan bearings than can cause it to seize slightly. As a consequence the power delivered by the resistor is not always sufficient to get the motor going. Others have temporarily bypassed the blower control module temporarily to kick start and free the motor up.

See the thread here - it will be very much similar to your DS5:

viewtopic.php?p=673222#p673222

Hi Marc,

Thanks for the reply.

1) I do believe these work, as throughout the years when the air hasnt been blowing, as i drove i would put down my window's slightly to help create an airflow draft passively through the car. I done this if there was any internal mist building up on the windscreen, sometime's I would notice that no climate zone is selected on the dial and when i would select the windscreen the mist would begin to dissipate after a few moments.

2) I havent tried either side independently of the other but i have adjusted the temperature while engine is at temperature for both sides (mostly in scenarios like the above) and would feel the air that drifts through would get warmer as i increased the temp.

3) I had looked through the other threads but wasn't entirely sure what would be relevant etc is the BCM for the DS4 also located behind the dash plastics in the passenger footwell of a right hand drive? Would you know how much on average a replacement BCM normally costs? Apologies as I am not a mechanic and the most electrics I have ever worked on in a car was replacing control modules for my Renault Megane 2004 electric windows.

4) Would you have the information on the bypass that I could use to try and test the fan in my DS4? I seen someone talking about pin 17a but i wasnt able to see the exact post that they were referring to for the bypassing.


I am hoping it is the BCM as it seems like its the easiest fix. But with how this was an intermittent fault that tended to mostly show its face during the colder seasons has me fearful its a ceased bearing within the blower unit.