Radiator Cooling Fan Operatation - With Ac On

[Guest Sharan Driver]

Hi,

 

Trying to fault find non-working Air-con on 1.9TDI 97 Sharan.

 

Had the infamous Flashing errors on Climate control. Had an AC specialist look at it and they replaced Receiver/dryer as this was leaking and refilled. Got rid of Flashing codes by removing bettery for 5 minutes. The system worked OK for about 2 weeks.

 

Now on selecting AC, there is no cooling at all. ( Outside Temp about 10C) and the 2 radiator fans come on full blast. This is even with the engine cold. Switching AC off, the fans go off. I can not see a direction connection between the 2 on the TIS. Only other thing not working is the booster heater ( although this has never worked)

 

1) Can anyone confirm whether this is normal behavior or not ?

 

 

Thanks

 

 

Chris

[charles]

i had a similar problem. the cooling fan running when engine was cold. turned to be a blown fuse (1 of the 2 big fuses for each cooling fan, fuse box at batteryroom)

[ridway]

The main coolant radiator and aircon condenser fans are controlled by both the cooling system temperature and the aircon system pressures which are proportional to condenser temperatures. These running at high speed immediately on switch on suggests there is a fault.

 

Given the information you have supplied my first checks would be to find out if the electric solenoid clutch on the aircon compressor is activating. If it is, this suggests there is refrigerant gas in the system. The difficult part is determining whether this is the correct amount. Two weeks of successful operation and then a failure does suggest you still have a leak, somewhere. You may have slowly been loosing the gas over this period.

 

I would suggest that you ask your AC specialist to recover and weigh the gas in the system and check it tallies with the amount introduced a fortnight ago. If it is down then further leak checks need to be carried out using a dye or electronic sniffer. Do not attempt to keep using the system if it is low on refrigerant because moving parts within the system do not get lubricated successfully and can quickly damage the compressor.

 

As a general rule of thumb when the aircon is switched on, the compressor clutch should engage and run more or less constantly if there is a maximum demand for cooling and it is a warm/hot day. It is however, normal for the clutch to drop out occasionally under automatic system control. What is not normal is for the compressor clutch to fast cycle on and off in a very short period of time (< 5 seconds). This can indicate both a lack of refrigerant, blockage, moisture, too much of a charge and several other faults not discounting the electronics and control.

 

If the compressor is not engaging then it is almost certain that you ref gas has leaked away and the pressure switch has shut down the system. Look for the centre of the pully turning on the compressor to determine if the clutch is engaged. Still = off, rotating = on. This sometimes fools the unaware into thinking that because the outer pully is turning the compressor is running.

 

From what you say I think you still have a leak. Once fixed I think the analogue and digital bits will sort themselves out and the fans will work as designed.

 

Best of luck

Rich

[seatkid]

On Mk 1 the fan (it only got one) comes on constantly at half speed when A/C is selected irregardless of whether its cold/working/etc.