Aircon problems

**caldirun** · 10-08-2019,10:12 AM

I am having problems with my aircon, it works well when on tickover but does not cool when revs climb over 1200. I have checked with VCDS, the solenoid valve duty cycle stays at 60% and the current at 0.6 A but the discharge pressure drops from 15 Bar to 5 Bar, the compressor status stays at on, no fault codes are logged. At first I thought it was the safety clutch slipping at higher revs but if I put a spanner on the centre nut I can turn the pulley so I think the clutch is fine. I am convinced it is a faulty solenoid valve not controlling the swash plate angle when the revs increase, has anyone had these symptions with a faulty solenoid?

**nevo** · 11-08-2019,04:16 PM

I would get some gauges on the hi/low sides and see the actual pressure,could be short of gas.

**Crasher** · 11-08-2019,08:13 PM

Have we! The number of these modern variable displacement compressors we change is ridiculous, the MQB platform is particularly prone.

**caldirun** · 12-08-2019,07:21 AM

Originally Posted by nevo

I would get some gauges on the hi/low sides and see the actual pressure,could be short of gas.

VCDS give pressure readings, these are fine untill the revs climb.

**nevo** · 12-08-2019,01:35 PM

I would say if the discharge press drops to 5 bar there's a insufficient gas on the suction anyway if you decide to change the solenoid valve you'l have to evac the system so you can check what the actual pressures are.

**caldirun** · 12-08-2019,05:41 PM

Originally Posted by nevo

I would say if the discharge press drops to 5 bar there's a insufficient gas on the suction anyway if you decide to change the solenoid valve you'l have to evac the system so you can check what the actual pressures are.

My first thought, I had the gas topped up 3 weeks ago, it made no difference. I think the extra force on the swash plate due to the revs increasing is sufficient to overcome the faulty valve and square up the swash plate on the shaft thus producing zero discharge, I will get back and report what I find.

**Crasher** · 13-08-2019,11:01 AM

I saw that on a T5 a few weeks ago, it was the compressor.

**caldirun** · 13-08-2019,05:39 PM

Hi Crash, I hope you don't mean that you changed the control valve and it still did not work! or do you mean that you just changed the compressor to make sure it did not come back in?