[90Horses]

Originally Posted by VCheng

Okay, now it is getting interesting.

Let us step back. Has anyone actually put in a thermometer in the different vents to see the actual readings of the air coming out with AC at full blast?

VCheng.Vecto Fiat techicians are using a thermometer which looks like the below image.

Technicians fix the car and check the corresponding vent's temperature, they have been doing this as part of their process. I have noticed vent temperature of a Punto to be 6 degrees if acc temperature was set to 18 degrees.

[VCheng]

Originally Posted by 90Horses

VCheng.Vecto Fiat techicians are using a thermometer which looks like the below image.

Technicians fix the car and check the corresponding vent's temperature, they have been doing this as part of their process. I have noticed vent temperature of a Punto to be 6 degrees if acc temperature was set to 18 degrees.

Good. So what are the readings for all the vents?

[90Horses]

Originally Posted by VCheng

Good. So what are the readings for all the vents?

I have not recorded the temperature of all the vents VCheng, usually the vent temperature will be in single digits.

Originally Posted by sagarpadaki

Does punto/linea not have a mechanism/slider switch which will block the air coming from that particular vent? If the vent has that option keep it closed till the problem is rectified. At least it will solve the sweating problem

Yes Sagar, Punto has the slider switch, I used to close this vent until I gave my car to Vecto for issue resolution.

Originally Posted by Jeroen

So you still need to figure out if the various valves open and close appropiately. A properly kitted out workshop migh have a little endoscoop they can stick into the various airducts to see what goes on. (e.g. something like this https://www.machinemart.co.uk/shop/p...s-inspection-c )

If they dont have one, I would try and have the complete HVAC unit hooked up to the car, but try and remove the various air ducts. You want to try and see the various actuaros/flap and so move, open, close. that might give further indication what goes on.

Good luck and let us know what they find.

Jeroen

Thank you for the suggestions Jeroen, I will sure let all know. They do not have a endoscoop, I think they would not have known one. I initially suspected evaporator coil, hvac control module, actuators and asked them to invesigate part by part. The above said parts come as as single piece, which is called HVAC unit by FIAT, I will try to get a picture of the spare the next time I visit Vecto, they replaced it with a new one and still issue exists.

[VCheng]

Originally Posted by 90Horses

I have not recorded the temperature of all the vents VCheng, usually the vent temperature will be in single digits.
............

Yes, that means the cooling is good. But what is the variation by which the central vents are warmer compared to the other vents? A degree or two might be well within the range allowed by the design. If more than that, then it requires a solution after investigation. Where does the heater core reside in that box and has its proportioning valve been checked?

[90Horses]

Originally Posted by VCheng

Yes, that means the cooling is good. But what is the variation by which the central vents are warmer compared to the other vents? A degree or two might be well within the range allowed by the design. If more than that, then it requires a solution after investigation. Where does the heater core reside in that box and has its proportioning valve been checked?

Variation between the left central vent with other vents was 7 degrees. Heater core lies in that HVAC unit, but I am unsure if they have checked the proportioning valve. Only thing that they have told me is HVAC unit cannot be separated into parts as it is a big unit and it cannot be investigated part by part at the dealership. For my car HVAC was a prime suspect and dealer has changed the part under warranty.

[VCheng]

Originally Posted by 90Horses

Variation between the left central vent with other vents was 7 degrees. Heater core lies in that HVAC unit, but I am unsure if they have checked the proportioning valve. Only thing that they have told me is HVAC unit cannot be separated into parts as it is a big unit and it cannot be investigated part by part at the dealership. For my car HVAC was a prime suspect and dealer has changed the part under warranty.

7 degrees variance is too much. With a new unit in place and presumably good, I'd check the heater core and specially its proportioning valve, which usually lives on the other side of the firewall. Assuming that checks out, I would then check for potential kinks or blockages in the ductwork and around the filter. Is the volume of the air in that vent okay or is that different too?

[ajaypjayaraj]

Have faced the same problem and like in your case, after the first diagnosis by the A.S.S. guys, they suggested to replace HVAC unit. But upon further investigation by myself with VCDS repeatedly, found that the individual vent temperature sensor was faulty and was giving intermittent fault signals. Initially, even they thought that it could be some flap not working properly or something just like you did. That does make sense. But in my case, the temperature sensor of the particular vent was replaced and problem solved. Nothing else had to be changed.

[VCheng]

Originally Posted by ajaypjayaraj

Have faced the same problem and like in your case, after the first diagnosis by the A.S.S. guys, they suggested to replace HVAC unit. But upon further investigation by myself with VCDS repeatedly, found that the individual vent temperature sensor was faulty and was giving intermittent fault signals. Initially, even they thought that it could be some flap not working properly or something just like you did. That does make sense. But in my case, the temperature sensor of the particular vent was replaced and problem solved. Nothing else had to be changed.

Do the vents have individual sensors in this car?

[ajaypjayaraj]

Originally Posted by VCheng

Do the vents have individual sensors in this car?

Not sure about this car but the problem mentioned in thread title reminded me about similar problem faced in my Skoda Yeti which has temp. sensors for each vent.

I discovered it when I decided to do the fault finding myself. Skoda A.S.S. came up with all sorts of suggestions to change compressor and HVAC unit and all. But I knew they had no clue as to what was the real problem. Did frequent VCDS scans and picked up one of the vent's temperature sensor throwing fault signals intermittently. The funny part is, after all this, I told the A.S.S. guys to order the part for that particular vent and after few days when I enquired, the reply I get is that they cannot find the part number for that sensor. Then I dug it up myself and gave them the part numbers of different sensors for each vent (Basically only 2 types were there out of which among the 2, only the shape was different, one was straight and other one was an L piece) and then they placed wrong order I patiently told them to re-order correct part. While connecting, I made sure the correct sensor went in the correct place by doing the work myself in front of their technician. And that is how they solved the problem for me. Anyways, issue was solved. Yeti has dual zone temperature setting and have temp. sensors in centre as well as side vents.

[VCheng]

Originally Posted by ajaypjayaraj

I discovered it when I decided to do the fault finding myself. Skoda A.S.S. came up with all sorts of suggestions to change compressor and HVAC unit and all. But I knew they had no clue as to what was the real problem. Did frequent VCDS scans and picked up one of the vent's temperature sensor throwing fault signals intermittently. The funny part is, after all this, I told the A.S.S. guys to order the part for that particular vent and after few days when I enquired, the reply I get is that they cannot find the part number for that sensor. Then I dug it up myself and gave them the part numbers of different sensors for each vent (Basically only 2 types were there out of which among the 2, only the shape was different, one was straight and other one was an L piece) and then they placed wrong order I patiently told them to re-order correct part. While connecting, I made sure the correct sensor went in the correct place by doing the work myself in front of their technician. And that is how they solved the problem for me. Anyways, issue was solved. Yeti has dual zone temperature setting and have temp. sensors in centre as well as side vents.

You make a great point, but if one of the sensors were at fault, then it would affect one or the other side, not just one vent. Why not switch the sensors and see if the problem switches sides?

[ajaypjayaraj]

Originally Posted by VCheng

You make a great point, but if one of the sensors were at fault, then it would affect one or the other side, not just one vent. Why not switch the sensors and see if the problem switches sides?

Actually not just left and right vent sensors, there were multiple temp. sensors even within one zone (one side) like left vent, left foot well, right vent, right foot well, etc. in my case. The HVAC system must be measuring from multiple points within one zone to adjust the vent flaps for efficient cooling.

I did not swap temp. sensors due to 2 reasons -

1) Left one was faulty and was easy to access by removing the glove box. But right one is a pain to remove. So I didn't want those guys to rip apart my car to reach a sensor just to swap and confirm.

2) VCDS pin pointed the faulty sensor and so I just told them to order that part. It wasn't so expensive anyways.

[90Horses]

Originally Posted by VCheng

7 degrees variance is too much. With a new unit in place and presumably good, I'd check the heater core and specially its proportioning valve, which usually lives on the other side of the firewall. Assuming that checks out, I would then check for potential kinks or blockages in the ductwork and around the filter. Is the volume of the air in that vent okay or is that different too?

If my assumption is correct, proportioning valve is the expansion valve. This was replaced as part of high/low pressure pipe replacement, still issue was not solved. Volume of air was fine, only the temperature was different. Today, they replaced pressure pipes b/w compressor - condenser and condenser. After that the temperature difference was 2-3 degree, which was not the desired result and they have decided to replace compressor tomorrow and let me know the result.

[VCheng]

Originally Posted by 90Horses

If my assumption is correct, proportioning valve is the expansion valve. This was replaced as part of high/low pressure pipe replacement, still issue was not solved. Volume of air was fine, only the temperature was different. Today, they replaced pressure pipes b/w compressor - condenser and condenser. After that the temperature difference was 2-3 degree, which was not the desired result and they have decided to replace compressor tomorrow and let me know the result.

The proportioning valve is very different than the expansion valve. Please do let us know what the results are. This is intriguing.

[90Horses]

Originally Posted by VCheng

The proportioning valve is very different than the expansion valve. Please do let us know what the results are. This is intriguing.

Oh i was not knowing that, where does this proportion valve sit? I will let you know the results tomorrow.

[VCheng]

Originally Posted by 90Horses

Oh i was not knowing that, where does this proportion valve sit? I will let you know the results tomorrow.

The proportioning valves sits in the piping to the heater core and controls the flow of hot water into the climate control unit according to the controller's commands.