911 2

Switched the air con on today and the fan at the front is definitely switching on and off runs for a few secs then stops then restarts, the compressor does come on and stays on, one of the aluminium pipes are cold the other is normal temp so i presume there is refrigerant present this was topped up a few months ago
despite this the air coming out of the vents is no colder than with the air con on
any suggestions, could the fan switching on and off be causing the problem

jeffnudd

Sounds like its working to me, have a look at the cold aircon pipe to see if its dripping with water, that should give you some indication as to whether it needs charging again, i normally advise most people in regular cars to have it checked and charged every 2 years because most people do not use aircon in the winter months and leaks through the seal on the compressor very slowly.
Check with a thermometer in the vents, if i remeber rightly it shoub be between 7 and 9 degrees with air con on full wack.

Hope this helps.

911 2

mo way 7 degrees the air is the same regardless as to whether air con is on or off
would the fan switching on and off cause bad air con performance

jeffnudd

No the aircon condensor fan is supposed to switch on and off all the time, if it did not the condensor would simply overheat, the amount of heat that is generated is massive, almost as much as a regular radiator in a water cooled car on tickover for an hour.

The air con temp is from memory around 7-9 degrees, that my friend is cold.
I am not sure if the system on a Porsche has a pollen filter? maybe someone here could tell us, but if it has it maybe blocked up causing air restriction? or your heater box servos may not be working correctly?

try a search for aircon in the search bar.

911 2

my left blower does make a funny noise
with nregards to the fan you may want to get another opinion as i ahve asked a few reputable sources and all have said the fan on the air con rad should always be on

Computamedic

AFAIK you are correct in assuming that the condensor fan should run on slow speed continuously. On/off cycle for a few seconds is a sure sign that the ballast resistor is toast!! It sits on top of the condensor and is known for corroding and disintegrating. It's a tricky job to get to but not expensive.

Regards

Dave

jimq

pollen filter came on the 993

911 2

does the switching of the fan to on anf off have a considerable decrease in performance on the air con

Computamedic

It's difficult to say. If the ballast resistor fails to open circuit (as I guess it would) the CCU would command the condensor fan to run at slow speed but the open circuit resistor would leave the fan off. From my experience of the same problem the fan seems to come on immediately at high speed and, within seconds, switch off, only to repeat the cycle within seconds again.

If the purpose of the fan is to induce air flow to aid the condensation of the refrigerant in the condensor you would guess that it would have little overall effect since the air is still flowing - albeit it in short fast bursts rather than a slower steady flow. It doesn't SOUND great - but I doubt it alters the effectiveness of the a/c system too much.

Regards

Dave