Thread: high pressure switch???

ok ,,,where is the high pressure switch???aircon fault reader says that it is open so wont engage the compressor ...wondering if it is the switch or something nasty and expensive??oh its and a4 1.8t sport....B5...97

Will probably find you have no aircon gas in system. High pressure switch will show as being open/short to earth if this is the case. Check for signs of damage to front condensor (On front of radiator)eg stone damage etc. Take it to specialist only to repair regas etc.
Also to answer your question. High pressure switch is fitted on O/S of Condensor, behind front bumper, below front o/s headlamp area.

The high pressure switch will NOT be open/short to earth just because you have no gas in the system. It is the job of the low pressure switch to determine that.

Unless you've recently had some work on it it's more likely that the switch itself has simply failed.

Not sure how expensive they are though. It's quite likely that a specialist will have to vaccum down the system to make the swap. That's where it costs more than the part itself!

This car has a dual switch located behind the bumper grille on the drivers side. This fault will be logged it is not connected. If work to the front end has been carried out recently it can be left off by mistake. If it is connected lack of gas is the most likely cause. Check for leaks as previously mentioned.

Originally Posted by mach1tl

This car has a dual switch located behind the bumper grille on the drivers side. This fault will be logged it is not connected. If work to the front end has been carried out recently it can be left off by mistake. If it is connected lack of gas is the most likely cause. Check for leaks as previously mentioned.

It may well be a dual switch but lack of pressure should not cause a high pressure fault. Unless Audis work in a frankly stupid way.

Originally Posted by staz1000

It may well be a dual switch but lack of pressure should not cause a high pressure fault. Unless Audis work in a frankly stupid way.

Air con (high) pressure switch is called this simply because it is fitted on the high pressure side of the air con system. It will read approx 5bar when compressor switched off and approx 9 bar when compressor is swiched on at full cooling output it is responsible for for feeding information back to ECU on pressures. If pressure gets too high or too low then compressor will be switched off by ECU and fault will be logged in both cases. (There is no other pressure sensor fitted to the system). Not so stupid when you understand how the system actually works.

I find this discussion very informative and of much assistance to me. It will provide relevant answers to my queries. Thanks!!

Originally Posted by me8cat

Air con (high) pressure switch is called this simply because it is fitted on the high pressure side of the air con system. It will read approx 5bar when compressor switched off and approx 9 bar when compressor is swiched on at full cooling output it is responsible for for feeding information back to ECU on pressures. If pressure gets too high or too low then compressor will be switched off by ECU and fault will be logged in both cases. (There is no other pressure sensor fitted to the system). Not so stupid when you understand how the system actually works.

I hadn't seen this reply until now. Are you saying that there isn't a low pressure switch whatsoever?

Hi Guys.

My switch failed this week. It caused the ECON button to stay on. So stopped the Air con to kick in. Had the guy out to day to replace and refill system.

Cost me £185.00. GULP. Took him about 2 hours to so.

If thats of any help.

tony