Air Con problem (rpm dependant?)

[caqpitancombo]

So, being here around 41°C in these days,
my 172 air con is not helping that much keeping me from sweating.
Thought it need to be regased or topped up.
No, was about perfect.
In the traffic seemed just fine, not as cool as Artic Pole, but fine.
But as I hit the MW, temp coming out of the vents went up, no matter what temp I set in the automatic climate control, recirc didn't help nor rising the speed of the fan, air was warm, not cold.

Compressor is kicking in, you can hear hit clearly at idle, if you hit the button.
Until you stand still, everything is about fine, as you move, you start to sweat, a lot.

So I made this test:
fitted a temp sensor in the central vent
at idle you can hear and feel the compressor kicking in
and the temp lovers until 9 or 10 degrees in a few seconds

if you slowly rev the engine (neutral, standing still) until 3500 rpm or so, everything is ok, temp stays around 9, 10, 11 or so,
if you go over 4000 the temp starts getting higher and higher
you lift off the throttle and leave it at idle
in a few seconds, you hear the compressor kicking in AGAIN

tested this many times, confirmed all the times
at about 4000 rpm the compressor is clearly disengaged
you cannot hear it disengaging,
'cause the engine sound obviously covers it
but you can clearly hear it engaging again at idle

I thought this was due to the Renault Sport Ecu,
in fact, partially it is,
switching quickly back to stock ecu,
it behaves the same, except that the limit is not 4000 rpm but around 6000 (had not so much time to find it exaclty)

has anyone ever find out this?

 

[Lagerlout]

Don't know if you've sorted this or not, but my 172 did exactly the same thing after fitting the R-Sport ECU, a few years ago now. That was one of the reasons why I binned it off, as well as my cruise control stopped working.

The same symptoms also re-appeared after remapping with an RS Tuner, even if i couldn't hear the 'click', i could feel the compressor kicking in and out.

I reported it to Henk from Fastchip and he sent me an updated cal file and it's as sweet as a nut now, no problem. Guy's a legend.

I'm pretty sure the standard ECU is supposed to cut the compressor out at about 6500 rpm. Is yours a late (2003) 172 by any chance?

 

[Lagerlout]

Just checked the manuals, compressor operation is prohibited above 6000rpm.

 

[caqpitancombo]

Did another test today
using a multimeter connected to the compressor +12v wire

at idle shows 13.8 volts, as it should
if you rise the revs, slowly,
voltage drops: 12.5, 12, 11, 9, 8 after that goes to zero
at idle, in a few seconds, again the compressor kicking in and 13.8 volts on the display

if you hit the pedal hard, even if not hitting the 4000 rpm threshold, voltage drops to zero
at idle, the compressor in again and 13.8 volts

seems definitely the RS ecu is cutting the compressor
I think that is due to give more power in any condition
, will have to use the other car, it is impossible to use the Clio without sweating as hell on the Sparcos