My A/C System does not work. I have checked the voltage to the high pressure sensor and it seems to be fine. But how do I know if the pressure sensor works? or how do I test it?

 

I got this diagnose fault:

 

Self-Diagnosis Log

Friday, 08 August 2014, 15:03:43:0

VIN Number: TMBGP21U738700031 License Plate: 

Mileage: Repair Order: 

Chassis Type: 1U - Skoda Octavia I

Scan: 01,02,03,08,15,16,17,19,22,29,35,36,37,39,46,56,76

 

Address 08: Auto HVAC Labels: 1Ux-907-044.LBL

Controller: 1U1 907 044 A

Component: CLIMATRONIC C 2.0.0

Coding: 11000

Shop #: WSC 31480

VCID: 301393C3E33B

1 Fault Found:

00792 - A/C Pressure Switch (F129)

35-00 - -

It could be the switch, it could be a blockage or the system may just need recharging. Without knowing the pressure in the system you can't test the switch.

It could be the switch, it could be a blockage or the system may just need recharging. Without knowing the pressure in the system you can't test the switch.

Is it possible to read the pressure in the system through the Climatronic unit (diagnose)? Or do I need to it manually with some measuring  equipment?

Is it possible to read the pressure in the system through the Climatronic unit (diagnose)? Or do I need to it manually with some measuring equipment?

A manifold gauge set or the dials of a recharge station will give you the high and low pressures. Can you find a place that recharges a/c systems and ask them if you are low on gas?

The only way to know if its low on gas is to evacuate the whole system and measure how much the gas weighs. AC refrigerant is added by weight and not pressure. The system could have loads of pressure and not much gas, take my Audi for example. I had the AC regassed 2 weeks ago as it was not working properly. The machine removed 700 grams of gas from the system, they added the correct 620 grams of refrigerant and the system is now really cold. Some of the gas extracted was the correct R134a, but some was obviously a mixture of other gasses.

Okay thx for your answers. I think my A/C system need to regassed then. 

 

 

The only way to know if its low on gas is to evacuate the whole system and measure how much the gas weighs. AC refrigerant is added by weight and not pressure. The system could have loads of pressure and not much gas, take my Audi for example. I had the AC regassed 2 weeks ago as it was not working properly. The machine removed 700 grams of gas from the system, they added the correct 620 grams of refrigerant and the system is now really cold. Some of the gas extracted was the correct R134a, but some was obviously a mixture of other gasses.

You have to remember, we are only trying to determine if there is enough pressure to operate the pressure switch, as the fault code is for the pressure switch.

There are tables of static pressures against ambient temperature, but you are right, you would choose to charge by weight as it's more accurate.