Independent Renault Forums banner
21 - 37 of 37 Posts

·
Registered
Joined
·
18 Posts
Discussion Starter · #21 ·
I'll try to explain better.

The cabin temp sensor reads out a value of approx 20 degrees. This is correct.

With this cabin temp, we set the climate control to 26 degrees. Then hot air blows out.

But when we set the climate control to 25,5 degrees, cold air blows out. This does not seem correct as the cabin temp is less than that. The system should then blow hot air to maintain that temp.

I do not know what the demanded position of the throttle is. But it seems odd that it closes fully when the climate control is turned down 0,5 degree and the cabin temp is less than what the climate control is set to.

That is where we wonder if there is another unit that can influence this as the climate control unit seems to be okay.

Also, since the throttle goes from 100% open to 100% closed it does seem like it is not stock (since it can move all all way from hot air to ice cold air).
 

·
Technical Supremo.
Scenic II, 2004, K4MW761, DPO
Joined
·
6,478 Posts
I'll try to explain better.

The cabin temp sensor reads out a value of approx 20 degrees. This is correct.

With this cabin temp, we set the climate control to 26 degrees. Then hot air blows out.

But when we set the climate control to 25,5 degrees, cold air blows out. This does not seem correct as the cabin temp is less than that. The system should then blow hot air to maintain that temp.

I do not know what the demanded position of the throttle is. But it seems odd that it closes fully when the climate control is turned down 0,5 degree and the cabin temp is less than what the climate control is set to.

That is where we wonder if there is another unit that can influence this as the climate control unit seems to be okay.

Also, since the throttle goes from 100% open to 100% closed it does seem like it is not stock (since it can move all all way from hot air to ice cold air).
I understood the problem you experience, but I am asking about
since the throttle goes from 100% open to 100% closed it does seem like it is not stock (since it can move all all way from hot air to ice cold air).
This is the cause.

So again - did you look at the mechanical integrity of the flaps inside the car that directs cooling/heating?
Are they able to move through their whole range and can you see the movement of the "throttle goes from 100% open to 100% closed" action?

The issue is whether the computer instructs "throttle goes from 100% open to 100% closed" or is the flap/throttle position measured as "throttle goes from 100% open to 100% closed"
 

·
Technical Supremo.
Scenic II, 2004, K4MW761, DPO
Joined
·
6,478 Posts
IMO the "throttle" is a misnomer (on most vehicles anyway) - it should be termed a simple flap - that's why I keep asking about the flaps. They are all located on the central heat echanger/evaporator unit under the dash behind the controls you use to set fan and temps.

You have either an incorrect instruction from the AC computer going to the flaps or there is wrong feedback information about the flaps' positions reaching the computer (broken flap/mount/encoder etc etc)
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #25 ·
This is what is behind the climate control unit. There does not seem to be a way to open that box without unmounting the whole dashboard. Is that correct?
Electrical wiring Automotive exterior Gas Computer hardware Hood
 

·
Technical Supremo.
Scenic II, 2004, K4MW761, DPO
Joined
·
6,478 Posts
Never had to strip one of those myself so unfortunately cannot tell you what to do.
On that diagram, the 4 "mixer motor" items are normally connected to flaps that can move to direct air over the heater core or the evaporator core - I do not know the exact design/construction details of your specific unit.
From what I have seen on the net this is a major job - something like dash out:(
 

·
Registered
Joined
·
18 Posts
Seems like the image did not attach.
And I hade to delete it, goes against forum rules to post parts from Haynes Manuals
Pictures were of the Evaporator Sensor, located in the passenger side of the heater box (UK cars....driver's side on LH drive)
 

·
Technical Supremo.
Scenic II, 2004, K4MW761, DPO
Joined
·
6,478 Posts
While I am glad you got sorted we did warn right in the beginning:
I really think the scanner is the correct way to go now that you mention the compressor too.

One can guess and take chances otherwise but its going to be wasting time and money only imo.

Do check on the circulation flaps inside the vehicle for broken plastic bits on the hinges first though - if one or more of those flaps are mechanically challenged it could also cause real strange temperature control behavior

Thinking about it a bit more - if the compressor is switching off at around 2300rpm, then its quite possible the AC system is going into protection mode (trying to prevent icing of the evaporator)
......................... and as @rawill commented, in his case the sensor was the answer just as here.



One can simply no longer be productive during vehicle repairs without a scanner :geek:
 

·
Technical Supremo.
Scenic II, 2004, K4MW761, DPO
Joined
·
6,478 Posts
Well...the scanner did not tell anything. The problem was solved thanks to a comment from a member in another forum that had had the same problem.
The scanner will not bring up an error for that faulty sensor by default - as long as it fails in a way that it still is producing readings within an allowed range of values there will be nothing to complain about or to create an error from ...................

The scanner operator needs to look at the evaporator temperature reported and consolidate THAT with what is happening on the compressor and the interior of the vehicle - he must know what to look for else he will miss the issue just as happened here.

That comment about 2300rpm killing the compressor you made and I queried? ............... if the scanner operator knew what he was doing he would have immediately jumped on that right in the beginning
 

·
Technical Supremo.
Scenic II, 2004, K4MW761, DPO
Joined
·
6,478 Posts
The scanner is your friend now - seriously - if the compressor gets stopped at a specific engine speed and evaporator icing is now known to not be the cause (??) , then its also possible the system is overfilled and the system goes into protection (killing the compressor) due to high pressure on the liquid line (condenser) .................... or the radiator fan/s are not working as designed ................ or the ECU is trying to give you all the engine power under acceleration ............... or etc
 

·
Super Moderator Technical Supremo Platinum Member
Joined
·
22,856 Posts
That makes sense.

The problem with the compressor kicking out at 2300 rpm is still present, it did not solve it to change the sensor.
Given the time of year, I suspect that the pressure within the system is getting to the point where it says enough is enough, the fluid is likely to be being supercooled..... pure guess but something I would be thinking and checking on.
Logic behind the guess is that a compressor doesn't kick out, it turns of because something has told it to and over pressure is one item that will do that.
 
21 - 37 of 37 Posts
Top