Air con compressor

[TightFist9]

2006 Mégane 1.5dci. After finally reinstating working air con last summer, noticed Friday no cold air from vents. Worked out compressor not engaging/working. Having changed condenser and dryer last summer plus obviously re-gas was not pleased. Gave it some thought and remembered I'd messed about with the fuses trying ( unsuccessfully ) to install a dash cam. Checked all these, all fine ,( is it ever that easy)? Pulled front bumper off (15 min job) to gain access to compressor. Can turn it by hand. Take 2 pin power supply plug off and use basic test light, no power supply. Run cables direct off battery to plug on compressor, audible click from it. Get wife to start car while I hold cables on , compressor starts running, fan cuts in, wife says cold air coming from vents. Wonderful, feel like progress. Grit teeth and strip battery etc etc out to get to other fuse box, check all fuses all ok. Now stumped....So have air con light illuminated in car, but no power electrical power supply to compressor, any ideas anyone please?

[VroomVroomClonk]

Hi,

There seems to be quite a list of parameters that the control systems in the car require to be correct before the air con will be "authorised" to operate. From memory they include refrigerant pressure, coolant temperature, engine speed, vehicle speed, fan speed and obviously air-con operation requested. I have checked every single one of them using Clip on my Megane, and despite everything being in the allowable values my aircon still refuses to be "authorised" by the control system! But my point is that any one of those monitored parameters could have a faulty sensor and prevent your aircon from operating even though your manual bypass shows that your system is actually operational. For example, the refrigerant pressure sensor is one area that does seem to cause a problem. If your sensor is faulty it could be telling the computer that you have no refrigerant and so preventing the aircon from operating, ... but that is just a suggestion.
Normally I'd say you need a proper diagnostic readout from CAN Clip to see which readings are out of range. However, as I have done that on my car and everything shows as fine but the aircon still doesn't work, ... it seems even Clip is not infallible in this case

[DougM]

I'm in the same boat. I had the car re-gassed last year from an unknown history. It went warm 3 weeks later, no luck with the garage so I left it. Now with some time on my hands I decided to have a go at fixing it. I checked the pressure it was 5 Psi, so I re-gassed it with a bottle of EZ Chill up to 30Psi at 23 degrees. The compressor came on and lovely hot air blew out of the ducts, not cold. I borrowed a CAN Clip from a friend, it says refrigerant level ok, aircon authorised and states the pressure is 2.8 bar with the engine off. Rising too 6 bar when the compressor is activated with no faults. That was yesterday, I came out today to check it and the manual gauge says 2 bar. The Clip says 1 bar, refrigerant too low. I switch engine on leave running and the pressure gets too 2 bar. The compressor still wont authorise even though 2 bar is the level it supposed too. I chuck some more gas in get it back too 2.8 bar. With the engine off it says refrigerant level correct, with the engine on incorrect. I leave it come back now its decided its correct and the compressor is running but only to 4.8 bar on the high side and the compressor sounds like it is cycling even though the refrigerant level is claimed to be correct. I also put some STP Sureseal in to try and cure the minor leak I thought I had. Not sure how much actually went in mind the high/low adapter seems to have stopped most of it going in. Oh joy.

[TightFist9]

Thank you both for your prompt replies. Shorty before getting the air con going last summer the car was in our local Renault indie garage trying to get the poxy windows fixed permanently. They are quite knowledge people , and the boss told me that despite the air con system being empty of gas for 4 years due to a leaking condenser , once the system was regassed there was no need to clear any codes, my understanding being that certain cars shut the system down when empty to protect the compressor. Both the air con engineer and myself were still surprised when it started working straight off after such a long time dormant. I'd also changed the receiver dryer, and the engineer had vaccumed out and pressure checked the system. It worked all during summer , much too my surprise. In 5yrs we have had all the joy of windows, air bag light, speakers, check injection ,water in door pockets and currently have the doors locking as soon as we drive off. Therefore not really surprised air con hasn't even,lasted a year. I'm still thinking that maybe,the fault is connected to me disturbing the glove box fuses trying to install a dash cam. The dash cam was another fail as it completely messed up the dab radio reception so pulled it out again. Despite checking all the fuses in glovebox and engine bay could only find one relay in the glove box panel so not sure if there are any more to check. I'm still leaning to running bypass cables to the compressor off an ignition controlled fuse with a switch ,if it works. Thanks again for your help.

[DougM]

Without a Clip diagnostic you really wont know what the computer thinks is wrong. It might be the pressure sensor or a constriction in the system preventing it from sensing the correct pressure. I have read a few articles from people saying they have been told that you need to re-activate it. I haven't come across it myself. Nor did I need to re-activate it mine after it had been flat for months. The activation pressure for the sensor is 2 bar, maybe if you left the car running for 30 minutes on a sunny day with the AC off, then try it. The pressure should build up with the temperature increase, it might be enough to trigger it , Alternately buy a Clip from Ebay for £100 quid. I reckon it could save you that much in short order. The only specific fuse I know of which is aircon only and no other systems is the red 10 amp one in the engine bay, no 13 if memory serves.

[TightFist9]

Thanks Doug , you've given me some ideas. Tbh the car is a law unto itself ! Awhile back had the heater blower motor pack up . Spent an afternoon contorted in the passenger well , pulled the complete fan assembly out, tested it on a battery and it started working again ands been fine since.
As I said as soon as I ran power to the compressor air con kicked in again so I'll try your idea of running car. It's got to be something stupid.
Not sure about buying clip can, computers are not my strong point. Sounds a good idea , just scared I'd do more harm than good.
Can I ask how easy you found it to gas system yourself ? Would you need clip can to measure the amount of gas required?
Thanks again.

[DougM]

The actual process of regassing is dead simple. Buy a bottle of gas and gauge for it and for the Megane your need a Hi/Low adapter for the port which is about £7 on Ebay. Now how much you decide to put in will depend on your circumstances. On mine it was basically nearly empty so I simply put the whole bottle in. I know how much is in the bottle 520g and I know the Megane allows for a tolerance of +/30g based on a requirement of 550g. I have less in it because I lost some repairing the leak with Sureseal as well. The pressure gauge is a useful guide and in my case has identified a going bad pressure switch. The Clip will tell you what the switch thinks is the pressure. Also in my case there was also a recorded previous fault on the switch which I cleared. I should add if your system has been completely empty and open then your need to get it all vacuumed and replace the dryer et al.