Good job done. You have confirmed the fans are operating and the problem is not due to the heater system interfering so we can get to the diagnostics. Who knows, we might be able to show the dealer some tricks.
The 2 large fans are known as radiator and condenser cooling fans, with the radiator fan at the transmission side. They would only come on when the AC compressor is engaged or when the engine operating temperature is hot enough to activate the fan switch.
The main problem should be the compressor cutting out when vehicle is operating at low speed and there are a few possibilities.
1. Low engine idling speed.
What is the idling speed when engine is at operating temperature?
Is there any clicking noise from the engine and does the idling speed keeps fluctuating when it is happening?
You can check this when the AC starts blowing warmer air. Note if the AC switch green light is flickering for a start.
2. Weak compressor. The compressor is able to provide cooling only when it is turning at a higher engine speed and when slowing down or stopped, the engine speed is low thus the inefficient cooling.
To test this, when AC is not blowing cold, check if the compressor is engaged, visually inspect if the compressor clutch is engaged and note if the cooling fans are running.
If clutch is engaged and fans are running, increase the engine rpm to 2000 and note if the cooling efficiency is improved.
Did the dealer check the low and high pressure at idling and when rpm is increased to 2000 rpm? This test should be able to tell if the freon level is correct, any operational malfunctions and possble cloggings in the system.
3. Freon, lack of it or over filled. Lack of it would be the more likely cause as overfilling would have the compressor cutting in and out while driving as well and the cooling would not be good as well.
4. Inefficient condenser cooling. As fans are working, it could be the condenser fans sre clogged with mudm dirt etc so give it a viasual inspection to confirm this.
5. Electrical circuit or component malfunction. Test would have to be carried out and if you have a DVOM and is into DIY, we can assist in provding the procedures.
Check the above and if there are any information that you think can be of assistance, please let me know.
Was any repairs done prior to this happening?
When AC is not blowing cold, does it improve when the vehicle starts moving?
Saturday, August 8th, 2009 AT 9:47 PM