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Discussion Starter · #1 ·
Hi there.
Have a Laguna 2 from 2005.
Recently a problem has occurred.

The climate is only blowing hot air if set all the way up to 26 deg. If turned down to e.g. 25,5 deg, cold air is blowing. There does not even seem to be much of a difference from setting 16 deg or 25,5 deg.

So far I have checked the following:
  • water level is good.
  • cleaned temp sensor behind interior rear mirror. Fan is spinning.

Any idea what to do next?

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Technical Supremo.
Scenic II, 2004, K4MW761, DPO
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I'd say a Renault speaking scanner is required to see what the climate control temp sensor is reporting back to the climate control computer...................

Me? - I would guess the computer may be mad though......
 

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Discussion Starter · #3 ·
I'd say a Renault speaking scanner is required to see what the climate control temp sensor is reporting back to the climate control computer...................

Me? - I would guess the computer may be mad though......
Thanks for the reply!
The climate control computer, is it located on the climate control print card behind the climate control display? Is it common to see a mad computer since you say it that way?

(BTW - I also have troubles with the ac compressor cutting off when hitting 2300 rpm. Not to go into that in this thread, but is it also controlled by the climate control computer?)
 

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Technical Supremo.
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Thanks for the reply!
The climate control computer, is it located on the climate control print card behind the climate control display? Is it common to see a mad computer since you say it that way?

(BTW - I also have troubles with the ac compressor cutting off when hitting 2300 rpm. Not to go into that in this thread, but is it also controlled by the climate control computer?)
Yeah I dont know exactly where its located on yours but its probably integrated in the electronics behind the control buttons yes - but the compressor is also involving the ECU in operations (engine control and protection) .............

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) as a result of the flaps simply not directing air to where its supposed to go
 

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Super Moderator Technical Supremo Platinum Member
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My suspicion is that the sensor is kaput.
System is not seeing a reading or simply maximum so does not put heat in until you select max (26?) which may bypass the sensor.
As such not a mad computer but one that is confused.
But fully agree with LVR that a decent scan would confirm/deny
 

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Super fantastic Mod Technical Supremo Nice Guy
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take the casing off the rear view mirror and give the sensor inside a wipe
 

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Discussion Starter · #7 ·
Hi all, thanks for your replies!

I have a friend that will soon help me scan for info codes.

In the mean time I've found out that the radiator fan in the engine compartment is not kicking in. Tried to go up to 4000 rpm, and it was not moving. Could it be a bad temp sensor? Is it one of those connectors that I could try to bypass?

I have already cleaned the sensor behind the rear view mirror with compreased air, and it is spinning when ignition comes on.
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Technical Supremo.
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Well.. I was trying to find out where to look for it. So that is why I ask. Thought that was what to look for when the fan is not spinning?
?

Look for what exactly?
.............. and why?

The fan is electric and controlled by the ECU as a function of coolant temperature and requested AC operation
 

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Discussion Starter · #13 ·
I was told there was a temp sensor controlling it, and that the sensor might be dead if the fan was not starting up when reaching above 2000 rpm. I went on a drive for half an hour, and the fan was not spinning when I returned home. I tried to go to 2000 - 3000 - 4000 rpm in idle, and it was still not spinning. But from your answer I see that there is no such sensor, and that it might not be the way to conclude if the fan is working or not. That was the one I was looking for.

So what would be the steps to confirm / deny that the sensors controlling the fan works or that the fan itself works?
 

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Technical Supremo.
Scenic II, 2004, K4MW761, DPO
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Well ................. I really don't know why you are fiddling with the radiator fan to begin with.

If you want to check on it there is only one way to do it:


FWIW - the radiator fan has absolutely no link to the engine speed at all.
 

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Discussion Starter · #15 ·
Well ................. I really don't know why you are fiddling with the radiator fan to begin with.

If you want to check on it there is only one way to do it:


FWIW - the radiator fan has absolutely no link to the engine speed at all.
Ok, I read the thread, and to my understanding you basically needs to connect the tester to read the average temp to see if that corresponds with the specs on the temp sensor. In your case it was reading too low (only reading average if 79c while the spec said 89c), so you concluded that it was probably faulty, and due to this fault it also did not turn on the radiator fan. Is that correct?
If so I see all arrows pointing back to the tester 👍
 

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Hi there.
Have a Laguna 2 from 2005.
Recently a problem has occurred.

The climate is only blowing hot air if set all the way up to 26 deg. If turned down to e.g. 25,5 deg, cold air is blowing. There does not even seem to be much of a difference from setting 16 deg or 25,5 deg.

So far I have checked the following:
  • water level is good.
  • cleaned temp sensor behind interior rear mirror. Fan is spinning.

Any idea what to do next?

View attachment 194376
View attachment 194377
Almost certainly a sensor fault.

The one that determines the temperature inside the car, or the temp coming out of the unit.

Same issue on my Saab.

A scan identified the fault, as it should for you.
 

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Technical Supremo.
Scenic II, 2004, K4MW761, DPO
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Ok, I read the thread, and to my understanding you basically needs to connect the tester to read the average temp to see if that corresponds with the specs on the temp sensor. In your case it was reading too low (only reading average if 79c while the spec said 89c), so you concluded that it was probably faulty, and due to this fault it also did not turn on the radiator fan. Is that correct?
If so I see all arrows pointing back to the tester 👍

No.!

The coolant temperature sensor was and still is 100% ok in my case ............ read that thread again - the thermostat was faulty in my case - I replaced THAT so that the coolant temperature could be properly regulated - IT HAS NOTHING TO DO WITH THE FAN AT ALL - THE RADIATOR FAN ONLY GETS TURNED ON BY THE ECU IF THE COOLANT TEMPERATURE IS A FEW DEGREES HIGHER THAN THE THERMOSTAT REGULATING TEMPERATURE.

As I said in my first post already, yes, a Renault-speaking scanner will be needed to guide you

I'd say a Renault speaking scanner is required to see what the climate control temp sensor is reporting back to the climate control computer...................
- and fwiw - don't expect the chase fault codes necessarily either - you will need to analyse the in-car temperature reported by the sensor located inside the rear-view mirror as @ours2012 already suggested here
take the casing off the rear view mirror and give the sensor inside a wipe
Have you actually done that already and did it change/improve the AC's behavior?

I really still dont know why you are faffing with the radiator fan when your original problem description makes no mention of that :unsure:
 

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Discussion Starter · #18 ·
Hi there,

Just ignorere the radiator part. It is spinning when the climate is adjusted.

I had the tester on today and only two errors were found, both relating to the a/c pressure regulating valve. Seems like the refer to the same problem. I have included two screenshot (in Danish), but maybe you know the error codes? They are probably related to the compressor turning off at above 2300 rpm, but are they also related to the problem regarding no heat?

Yes, I did take out the sensor behind the rear view window and blowed it with compressed air. No change. Picture included of the state before it was blown.
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Discussion Starter · #19 ·
An update on this.
The tester is still not reporting any errors regarding the heating system.

Today we has the tester on and read out the cabin temp sensor. Reading seems correct.

We can also see that when the heating is turned up to max (26 deg), then the heat regulating throttle is at 100 % open. When we regulate the temp down 0,5 degrees to 25,5 degree, the heat regulating throttle drops to 0% open and cold air is let in.

We tried to change the heat unit (picture attached), but that did not make any difference.

Any idea what could be the case?

Is there some other climate computer located outside the unit in the picture that could cause this?

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Technical Supremo.
Scenic II, 2004, K4MW761, DPO
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An update on this.
The tester is still not reporting any errors regarding the heating system.

Today we has the tester on and read out the cabin temp sensor. Reading seems correct.

We can also see that when the heating is turned up to max (26 deg), then the heat regulating throttle is at 100 % open. When we regulate the temp down 0,5 degrees to 25,5 degree, the heat regulating throttle drops to 0% open and cold air is let in.

We tried to change the heat unit (picture attached), but that did not make any difference.

Any idea what could be the case?

Is there some other climate computer located outside the unit in the picture that could cause this?

View attachment 194642
View attachment 194643
Im confused ................ all of this must reference the current cabin temperature else its useless .............
We can also see that when the heating is turned up to max (26 deg), then the heat regulating throttle is at 100 % open. When we regulate the temp down 0,5 degrees to 25,5 degree, the heat regulating throttle drops to 0% open and cold air is let in.
Is that "throttle" value the demanded position? .............. what is the measured position?






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
 
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