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All pictures and texts in this web page are the property of nomaallim.com. Any use of any part of those contents without the written consent of nomaallim.com shall be subject to legal procedures as per international and local laws in the concerned country. Using the name "nomaallim" or "nomaallim com" or "nomaallim.com" in the text describing the unauthorized copied content shall not constitute an exception and shall be sanctioned in accordance to the effective laws and proceedings.
BEFORE YOU START
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DISCLAIMER:
Our pictorials are of informative nature and do illustrate works carried out by ourselves at our own premises for our own use and satisfaction.
Readers who envisage to carry out similar works inspired by the below method shall do this at their own risks and liability.
Our pictorials are of informative nature and do illustrate works carried out by ourselves at our own premises for our own use and satisfaction.
Readers who envisage to carry out similar works inspired by the below method shall do this at their own risks and liability.
NOTE: Although shown on a 2016 Citroën DS3 Phase 2, this car AC diagnostic method remains similar or identical on almost any vehicle, especially european cars.
Symptoms of a car air conditioner that does not blow air
A car air conditioner uses a cabin mounted unit to cool or heat air and distribute it in the vehicle.
Such unit is located underneath the dashboard and requires the removal of the latter for inspection and repair.
Air conditioning and distribution is done through motorized flaps, actuated by not less than three motors as follows:
I'm showing here the diagnostic of a 2016 Citroën DS3 which A/C had two faults:
The AC compressor starts normally regardless of the described air flow problems.
Such unit is located underneath the dashboard and requires the removal of the latter for inspection and repair.
Air conditioning and distribution is done through motorized flaps, actuated by not less than three motors as follows:
- One step motor for car A/C temperature regulation
- One step motor for distributing air towards the windshield (defogging) or towards the front aerators or towards the cabin floor or any combination of those.
- One step motor to activate the recycling feature, i.e. cut or allow the air coming from outside the vehicle
- The car A/C blower can be heard running normally but no air comes out of the aerators on the dashboard
- A/C blower still changes speeds but its noise at the highest speed is abnormal and still no air comes out of the aerators
- Air distribution is stuck at a particular position , it is not possible to modify it from defogging to front cooling to feet cooling
- When air comes out of any of the aerators, it is well cooled and the A/C compressor can be heard starting normally
- A/C air distribution flaps might be stuck from time to time, then work normally the rest of the time
I'm showing here the diagnostic of a 2016 Citroën DS3 which A/C had two faults:
- A permanent smell coming from exhausts of surrounding cars in heavy traffic, even when the air recirculation button is activated
- A blocked air flow from all aerators from time to time, resulting in the AC blower operating normally without having any air conditioned air flowing inside the vehicle, thus a total inefficiency of the air conditioner when such blocking occurs.
The AC compressor starts normally regardless of the described air flow problems.
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Visual inspection of the car A/C unit
Upon inspecting the A/C unit, I immediately noticed:
- A broken and missing foam seal between the incoming air duct and the AC unit, which explains why the air recirculation feature is not working; air coming from outside the vehicle goes to the cabin from that missing seal, before the air recirculation flap.
- Deformed and detached seals around the AC unit openings denoting that the dashboard had been previously dismounted but quite badly refitted in a manner that it was pushed upwards while rubbing against the seals; it is true that this vehicle was recalled for airbags replacement because it was initially fitted with the notorious Takata airbags.
Having taken off the broken part of the foam seal, I also noticed the traces of rodent teeth, which explains why this seal was damaged.
This means that debris from the foam seal are stuck for sure before the AC blower.
This means that debris from the foam seal are stuck for sure before the AC blower.
I further investigated how a mouse could have reached the seal and discovered that it had found its way from the pollen filter within the engine compartment. It is true that the decorative plastic grilles of the Citroën DS3 underneath the windshield wipers, do have diamond shaped opening that are big enough for a mouse to go through!
The issue of the air recirculation problem is therefore fully uncovered and the fix will include:
The issue of the air recirculation problem is therefore fully uncovered and the fix will include:
- Replacing the pollen filter
- Cleaning the duct and the AC unit from the seal debris that are stuck inside
- Replacing the foam seal between the cabin air intake duct and the AC unit
As far as the AC blocked air flow issue is concerned I will now diagnose and test the AC flaps actuator which consists of the following elements, shown in the second picture:
- The step motor
- The white plastic gear element, which moves each of the defogging, front and lower flaps when rotating.
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Manually testing the car AC air flow distribution flaps
I will first remove the step motor so I can operate the AC flaps gear with my finger and check for any hard point or deformation that could block the movement.
In this video, I show how the gear is moved in both directions while I watch the flaps.
All seem fine except some excessive noise due to the lack of grease which I will further investigate in the next step.
All seem fine except some excessive noise due to the lack of grease which I will further investigate in the next step.
Now this video shows how the grease on the AC flaps gear dried up or hardened making the operation quite noisy, also increasing the gaps and consequent noises, with a possible and potential risk of having a blockage:
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Starting the engine and testing the car AC electronic controls
I will now refit whatever can be refitted and connected despite the absence of the dashboard, in order to minimize the number of errors the car ECUs will generate upon reconnecting the battery and starting the engine. I will temporarily attach each of the AC control panel, instrument panel, steering column stalks, AC sun sensor and LCD display:
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This now allows me to start the engine and the AC of this Citroën DS3 in order to test the controls.
I'm showing here two videos, one with the step motor mounted and one with the step motor removed from the AC flaps gear assembly.
This allows me to check if there's any fault at the step motor or gear level.
I'm showing here two videos, one with the step motor mounted and one with the step motor removed from the AC flaps gear assembly.
This allows me to check if there's any fault at the step motor or gear level.
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Final result of the AC diagnostic and what are the required fixes
The above videos and pictures do show that there's no fault at any of the AC flaps gear or step motor.
The actuator is operating normally and so is the set of gears that allow to move (rotate) each of the air distribution flaps.
A lack of grease was noticed, also hardened grease, but this alone cannot cause the AC mechanism to get stuck at some position.
I did find the problem by intervening on the below screw, that fixes the actuating step motor to the AC flaps gear.
If this screw is too tight, the whole mechanism gets stuck; therefore and with time, also because the grease hardened and became sticky, the operation of this mechanism resulted in a tightening of the screw which leads to the AC flaps getting stuck and the AC air flow to be blocked. Click on the link further below for the fixes I applied and the final in-car AC testing prior to reassembling the dashboard.
The actuator is operating normally and so is the set of gears that allow to move (rotate) each of the air distribution flaps.
A lack of grease was noticed, also hardened grease, but this alone cannot cause the AC mechanism to get stuck at some position.
I did find the problem by intervening on the below screw, that fixes the actuating step motor to the AC flaps gear.
If this screw is too tight, the whole mechanism gets stuck; therefore and with time, also because the grease hardened and became sticky, the operation of this mechanism resulted in a tightening of the screw which leads to the AC flaps getting stuck and the AC air flow to be blocked. Click on the link further below for the fixes I applied and the final in-car AC testing prior to reassembling the dashboard.
