[marcjero]

Hi,

my ac is working fine but the air that comes into the cabin is not cold enough.
We checked the ac system pressures and it seems that the pressure doesn't build up high enough. Basically the max pressure is about 5-6 bar and when this value is reached the fans are starting and the pressure then drops.

I don't think there is a leak because the ac is still producing cold. I think that the ac pressure switch could be faulty then.

Opinions please ?

 

[jakejm79]

Make sure the low speed portion of the radiator fan is working. When its just working on high speed, the pressure will increase until the point the fan is commanded for high speed then the pressure will sharply drop (due to the fan cooling). What should happen is that the condenser temp and pressure remains pretty constant with the fan running on low, only high being needed for extremes.
Is the cooling any better when traveling at speed vs stopped?

 

[marcjero]

Hi,

my car has a nordic setup with single speed fan. I didn't notice a difference when stopped or driving. It's the same. It looks like it's working better just after a cold start.

 

[EdT]

You should evacuate the system and then charge with the correct weight. The system can be low on charge and it will still cool, but poorly.


The single speed fan turns on at a specific pressure, and then turns off once the pressure drops. I don't have the pressure numbers available right now, but they are in WIS.


Watching the pressure reported using a Tech II would be very helpful.

 

[marcjero]

Once aircon is enabled the fan kicks in within 10 seconds and prevents pressure to grow. The guy said me that the pressure is way too low and fan is preventing to reach the required level. I think that if gas was missing fan should not start so fast.

 

[EdT]

Once aircon is enabled the fan kicks in within 10 seconds and prevents pressure to grow. The guy said me that the pressure is way too low and fan is preventing to reach the required level. I think that if gas was missing fan should not start so fast.

Maybe there's too much gas in the system? Has it been charged recently, and if so, how?


The guy's explanation does not make sense to me. A properly charged system with a properly working compressor won't care if the fan is on or not. The increase in pressure created by the compressor will be all the pressure difference required. His explanation sounds like other folk tale facts.



You need a Tech II to read what is going on with the pressure switches in the A/C system.

 

[marcjero]

update : Looks like the ac is working pretty fine from a cold start and during about 15 minutes. After a while the compressor doesn't seem to work anymore.
I can see it with the vacuum needle not moving at all when engaging aircon.

Not sure if charging the system is a good idea.

update : please read this https://community.cartalk.com/t/air-conditioner-shuts-off-when-driving-but-works-when-stationary/28698

Today i drove a lot in the city and aircon was working fine even if outside temperature wasn't high. But when I reached a road and accelerated a bit the ac stopped working.

Question : is it a simple way to check if the ac control system is actually trying to engage the ac compressor ? Want to know is the issue is with the control panel or the compressor clutch. I ran the autocheck procedure, no problem found.

 

[marcjero]

Today I asked for a a refill of aircon system. It was done successfully as there was not evidence of leak. However the system pressure was very low before the service.

Result is that now air is much colder than previously.;ol;

But the aircon still stops working after a while driving. Switching the engine off doesn't recover the aircon.

I just noticed that the fan is now kicking in as soon as I activate aircon. The condenser is cold when this happens. When I stop aircon the fan still runs, it seems to run forever.
Is there a temperature sensor anywhere ?

 

[EdT]

Do you have WIS? It covers the various conditions the system needs to activate the compressor. To summarize:

1. The pressure in the condenser must be between 2 bar and 27 bar
2. Evaporator temperature must be > 4º C
3. Engine temperature must be < 126º C
4. Also the compressor itself has a shut-off if it gets too hot

You would need a Tech II to see which of these conditions is being violated.

 

[marcjero]

2. and 3. are fine. I can't test 1.and I don't have a tech2.

Strange t: blowed air is likely warmer than ambient temperature. Is it possible to easily check that the compressor is activated ?

 

[EdT]

If the compressor isn't running, then it's quite likely that the air your are pulling in has been heated by the hot engine and hood/bonnet. Also the heater core will still be hot and warming the air a little bit, even if the flap to it is completely closed. So, yes, air blowing out the vents will seem heated a little bit more than the usual outside air.



You may also want to check the temperature of the compressor itself. I assume that the A/C will start working again after the engine has been shut off for a while. That can also mean that the compressor has cooled off.


When the system was charged, was the proper amount of oil added?


The receiver/dryer also probably could use changing. However it may not necessarily come out easily.

 

[marcjero]

oil ???

 

[EdT]

There is some oil in the system to lubricate the compressor. You have probably lost some oil, between 15 and 30 ml. Depending on how the system was recharged, they may have added oil or not.



If the system is really low on oil, then that might make the compressor run hotter and shut off.



There are some people here that know the compressor system better, like jake. Anyway, from looking at WIS, if you put direct power to the A/C clutch but it does not engage, that would indicate that the compressor has overheated and the thermal protection has shut it off.

 

[marcjero]

interesting. Where is the temperature sensor of the compressor ?
They didn't mention they added some oil in the system.

 

[marcjero]

Just found this :
http://www.saab9000.com/procedures/ventilation/airconclutch.php

I will try this fix tomorrow.

 

[marcjero]

Just found this :
http://www.saab9000.com/procedures/ventilation/airconclutch.php

I will try this fix tomorrow.

Hi,

looks like this was the problem. I removed the last washer. Need a 14mm wrench not an allen key.