Interior temperature sensor reports correct temperature = how are you checking this

 

Using can clip, it is one of the readings of the climate control ecu.

 

Ours, any ELM can read that.

Jose, set your onboard comp to show current fuel consumption.
Usually it should be on 0,3-0,4 litres/hour. When AC turns compressor on, that goes up to about 1 litter per hour.
While driving your should feel that the engine is not as powerful when it turns AC compressor.

 

Jose, set your onboard comp to show current fuel consumption.
Usually it should be on 0,3-0,4 litres/hour. When AC turns compressor on, that goes up

Nice, thanks

 

Also, would be useful for us to know which car, which engine, auto or manual AC.
If you want you can have visual confirmation of compressor working. Just connect small, 2W and 12V bulb to the connector on compressor and place the bulb in cockpit. Every time compressor is on you will see bulb activated.

Has anybody checked cabin air filter?
Does you AC smell like old sneakers when you turn it on? If yes, it is possible that heat exchanger is clogged with filth, bacteria, even moss.

 

Also, would be useful for us to know which car, which engine, auto or manual AC

Megane 3 1.5dci 106cv BZ0B, auto AC
New filter, evaporator looks clean looking trough the filter housing. No funny smells.

 

Assuming you still have R134 in that thing..................

Evaporator temperature sensor reports correct temperature

Good starting point since you have CLIP ............... as a matter of interest what ARE you seeing here that is "CORRECT"l? ............ need something above dewpoint to prevent freezing of the coils so say 10C
If you are happy with the performance under 30C ambient in traffic, chances are good the problem is not here

PR037 Refrigerant pressure reports about 10 to 15 bar

and

The vehicle has been at two repair shops which found no issues (the first introduced some refrigerant gas)

Guessing you will find this to be the problem area .............
R-134a System Pressure Chart - AC Pro (acprocold.com)
If you are already hitting 15Bar on the HP side before the ambient gets to 30C, chances are the system is overfilled and simply goes into protection mode on overpressure and disables the pump




ALSO - if in traffic the engine coolant reaches critical temp levels even though the fans are working, the ECU will disable the pump too

 

If you are already hitting 15Bar on the HP side before the ambient gets to 30C, chances are the system is overfilled and simply goes into protection mode on overpressure and disables the pump

Good to know.
Any chance that compressor clutch is slipping on that model?

And for Jose. Did you check aux belt , it's tensioner? It is firmly grasping AC compressor?

 

If clutch is slipping it will not work at lower temps also (my guess/experience only) - the model BZ0B doesn't tell us if its a simple clutch driven compressor or a variable thing with no clutch at all (pump runs always).

Really easiest is to use CLIP and log engine coolant temp and AC refrigerant pressure during one of the funky 30+ ambient episodes - one will immediately be able start pointing intelligent finger(s)

 

Really easiest is to use CLIP and log engine coolant temp and AC refrigerant pressure during one of the funky 30+ ambient episodes - one will immediately be able start pointing intelligent finger(s)

Easy enough, will try that as soon as the weather permits. Portugal had a temperature drop this last 2 days.

 

Wasn't aware that MegIII would have variable compressor.

 

Me neither but the reference material suggest the possibility - I don't know for a fact - pics of the animal suggest a unit with clutch though but no engineering details available during my searches

 

Is that two speed fan on that car?

Thinking, if higher speed is busted, maybe it can't work when temp is high, for protection.

 

Tell us all about the fans' behavior (both) - when and at what speed and coolant temps - use CLIP to log

Im thinking the opposite - low speed engine cooling supposed to run - doesn't - AC pressure spikes and protection kicks in disabling AC
...............

 

Will perform the log tomorrow. Had a quick look at the fan behavior and indeed the condenser fan spins as soon as the AC is turned on (apparently single speed). The radiator fan always spins, normally slow and sometimes quick.

Checked the compressor model: Denso 6SEL14C 8200939386

Thank you all for the help

 

Raditor fan is just moving from air passing by it, from AC fan in front of it. Can't be that radiator fan is always ON.

 

Raditor fan is just moving from air passing by it, from AC fan in front of him. Can't be that radiator fan is always ON.

Can be yes, will try stopping it by hand, will report on the resulting finger count.

 

Don't even try that or you will have nothing to poke your nose with.

If you really want to make sure, use something soft, like piece of stiropor.

 

Most all vehicles I have seen will have the engine cooling fan spinning at low speed soon as AC pump is functioning/switched on.

The trick is to use CLIP and to monitor the ECU's issuing of the fan on/speed commands vs ambient and coolant temps ................ I am still betting that thing may be overfilled or a fan is not dong what its told

 

Most all vehicles I have seen will have the engine cooling fan spinning at low speed soon as AC pump is functioning/switched on.

In ancient history, when there was no fuel injection and only the most expensive cars had air conditioning, AC pump was, where I live, name for mechanical fuel pump on gasoline cars

My car has got only one fan.
Start the engine, fan is not moving. If I turn on AC, fan is turning even with a cold engine.
He has two fans, maybe only single speed. As soon as AC is turned on, AC fan is also on and it will keep moving as long as AC is on.
But engine fan does not follow that. If it's moving, it's from stream of air, no power to it. When engine needs to be chilled, fan starts to move with power and at much higher speed

 

Yes, to much pressure is most likely. Wether from fan or to much gas, that's the secret yet.
Faulty orifice would not care about outside temperature.

 

Hi all, sorry for the late reply, only now the temperature is enough for the problem to show again.
I have logged all of the injection ECU values I believe could have an influence on the issue. I'm attaching an excel (xls) containing the log (file extension set to txt to allow upload).
So while the issue is present with an outside temperature of 32 degrees CLIP shows that the cooling fan speed is set to high due to the AC requesting it (and is indeed spinning high), water temp is about 76C, the AC has the OK from the injection ECU to work, and the evaporator condenser pressure is about 7.8 bar.
All of the above looks fine except the condenser pressure which I think is to low. It is about 15bar with lower outside temperature though. I believe it should be the opposite right? The pressure should raise with temperature, what can be causing this?

Thanks

 

Hi all, sorry for the late reply, only now the temperature is enough for the problem to show again.
I have logged all of the injection ECU values I believe could have an influence on the issue. I'm attaching an excel (xls) containing the log (file extension set to txt to allow upload).
So while the issue is present with an outside temperature of 32 degrees CLIP shows that the cooling fan speed is set to high due to the AC requesting it (and is indeed spinning high), water temp is about 76C, the AC has the OK from the injection ECU to work, and the evaporator condenser pressure is about 7.8 bar.
All of the above looks fine except the condenser pressure which I think is to low. It is about 15bar with lower outside temperature though. I believe it should be the opposite right? The pressure should raise with temperature, what can be causing this?

So the ECU is doing the right and expected thing - AC on means fan must run and you confirm that happens.

Question now is:

AC on at ambient @ 32C you should see around 17Bar+ on the condenser (high-pressure line) and around 3Bar on the evaporator (low-pressure line) ............. again see

R-134a System Pressure Chart - AC Pro (acprocold.com)

I don't know on your particular vehicle which line is actually instrumented (or are they both?) ............. normally you only have the suction line (evaporator) instrumented (giving a pressure reading) nowadays.

As I said before - overfill will cause too high HP and LP pressures and protection will kick in - typically system will work when cold and not when hot ambient.

We need to get your terminology straight.

That log is useless - you need it in CSV format (not plain txt) so one can make pretty pics in eg Excel etc to look at and discuss

 

In order to confirm the theory with little effort:

Next time the AC stops working when ambient is hot - spray the condenser coils in front of the radiator with a garden hose - the radiator too no problem .................... if you see the AC starts working again you have the info you needed

 

If those are the only commands then I would see if mechanically the compressor is running with the clutch pulled in/engaged - if not measure the clutch voltage received - if 12V then suspect possible clutch failure at temperature ................ there have been reports on here too where this happened.

Did you try the water on the condenser and radiator experiment I suggested earlier? ................ perhaps you can run a lot of cold water over the AC compressor too while things aren't working and see if that can make it engage

 

There is no clutch as discussed earlier. Didn't try the water yet.

 

My bad ...............not able to remember everything on all threads carrying on for days with no progress

 

I'm sorry, believe me the lack of progress is very frustrating, but this is an issue which only occurs in very particular situations and as been around for years with no solution in sight

 

WRT to my comment about overfilling:

I think that you will get what I am talking about when I mention superheat and subcooling ..............

The idea is to have both figures on a well designed working AC system close to the same - iow to ensure you do not produce more unused subcooling in the condenser (too high a temperature difference to ambient) if the efficiency of the evaporator is such that one cannot ensure the complete (max) used superheat in the evaporator ...................

It comes down to this basic statement:

If you have a typical temperature differential inside the car of about 10C relative to ambient outside (iow what you actually experience) you need about that same differential across the condenser to equal the energy input (compressor) to the energy consumed (evaporator)