Aircon not working Golf FSI 2L 2005

[sunda]

Hi,

The air conditioning is not functioning in the 2005 Golf 2.0L FSI Automatic.

When I switch on the A/C and the blower, the A/C fan does not turn on. I'm uncertain if the compressor has a clutch; there is a control valve connected to the back of the compressor with two wires, but I don't see any other wiring connections to a clutch if one exists. When I turn on the ignition switch, I measure around 5V on one of the wires. I can see the high-side pressure switch, but I cannot locate the low-side switch.

There was very little refrigerant gas in the system. I safely evacuated and recharged it with Hychill Minus 30 after confirming there were no leaks during the vacuum process. However, the compressor did not engage, and I observed 80 psi on both the high and low sides. Additionally, the refrigerant paused halfway while entering the system.

I would greatly appreciate any assistance in troubleshooting this issue. Furthermore, if possible, please provide the wiring diagram for the A/C, along with the locations of the relays and fuses. Thank you!

[JustCruisn]

The compressor is variable displacement. No clutch like the traditional style. The issue could be the control value or the compressor.
The small radiator fan should run when ever the AC is on. The fan controller is built into the larger fan, this bit often fails too.

[sunda]

Thank you JustCruisn for your reply.

You are correct; it has been confirmed that the compressor is of the variable displacement type. I measured a 12V supply to the high-pressure sender and 8V to the solenoid valve. As you mentioned, it could be a faulty valve, and I would like to replace it. Is there any way to bench-test the valve before proceeding?

[MIG]

Check that the low-pressure switch hasn't tripped. Those solenoids jam internally so checking resistance is not a definite, so the only way to test them is with a gauge set.



Here is the TPI on the newer compressors, but if it's a variable unit, it will be very similar.

https://static.nhtsa.gov/odi/tsbs/2016/MC-10107210-9340.pdf

I got my local shop to reclaim the system. I replaced the valve; then got the shop to recharge the system.

$100 for the valve and $100 for the reclaim + recharge.

[sunda]

Hi Everyone,

I appreciate your assistance in troubleshooting my air conditioning problem.

I couldn't find the low-pressure switch in the AC system. I believe that this model may not have such a switch. If I'm mistaken, please let me know.

I believe the compressor control valve is functioning properly. It clicks when 12 volts are applied and shows a resistance of 11 ohms during the bench test. Additionally, when air is blown through it, it escapes, and it partially blocks when 12 volts are applied.
Given this, can I rule out a faulty valve and focus on troubleshooting the smaller fan behind the radiator? The fan doesn't spin when the AC switch is turned on.

Thank you!

[JustCruisn]

The fan doesn't spin when the AC switch is turned on.

Fix that first.

Do either fans run at all ? even with a hot engine ??


Big fan is engine cooling
Small fan is AC cooling.

The big fan has a controller built into it.
Small should run whenever AC is on. Large fan will switch based on engine temp.

The controller tells the smaller fan when to start. So if the small one is not running I would suspect either controller failure, or small fan failure.

You can test the fan directly by applying 12v to the fan. The small one pigtails off the large one, but the connector is on the radiator side of the fan housing. You need to pull the housing to get to the connector. Use thick wire as the fan pulls heaps of power and may burn out a thin jumper wire.
If that small fan runs with 12v directly I would be looking at the controller, if no sign of life then new small fan.

[MIG]

resistance of 11 ohms during the bench test. Additionally, when air is blown through it, it escapes, and it partially blocks when 12 volts are applied.

Did you take the valve out? If so, how much refrigerant was recovered, and was it low on charge?

If you have not taken the valve out, don't without getting the system discharged (professionally, keep those CFCs out of the ozone) the high pressure can be dangerous!

[sunda]

I bench-tested the radiator fans. When I applied 12 volts to the red and black wires with the brown wire grounded, both fans started spinning. If I grounded the green wire as well, the fans continued to spin.

However, when I connected the fans to the vehicle, they did not spin. I disconnected the connectors and made the connections as shown in the picture below, but there was still no movement. Interestingly, when I disconnected the green wire, both fans began to spin again and stopped once the green wire was reconnected.

In the vehicle's wiring harness, the red wire has 12 volts at all times. The black wire has 12 volts only when the ignition switch is on, regardless of whether the AC switch is on or off. I also noticed that the 458 relay is hot.

Doesn’t the green wire get disconnected somewhere else when the AC switch is turned on? Can I conclude that the fans and the fan control unit are functioning properly?

Do you think the problem lies within the AC control unit?

I would appreciate your help.

[sunda]

To summarize, I previously evacuated the small amount of gas that was in the system safely and then recharged it with refrigerant minus 30. Unfortunately, the compressor did not engage. I evacuated the minus 30 refrigerant from the system again and removed the compressor valve. During a bench test, the valve appeared to be functioning properly. Now, I am troubleshooting the issue of why the fans are not spinning.

I mentioned in my previous post what I observed while troubleshooting the fan issue. I am unsure where to jump in.

[MIG]

Sorry I missed that part, check out this post about the J293 module mk4 Fan Control Module (J293) chart and A/C tips | Ross-Tech Forums

It has a nice checklist of things to go over, the mk5 will be close still

The difference with the Mk5 is that the J293 is controlled digitally via the ECM on that pin T4x/3


Do you have a scan tool that can do output test?

[sunda]

The table does not match my model, except for the first four connections to the Fan Control Module. Additionally, I could not locate the corresponding fuses in my diagram. However, the fact that the ECU triggers the fans via T4x/3, and that the high-pressure sensor sends a signal to the fan control module, provides useful clues for proceeding with troubleshooting.

Thanks, Mig, for your cooperation.

I am unsure how to test the high-pressure sensor, so I will look it up online.

I connected a large fan that I purchased along with the module from the junkyard, and it behaves the same way as the existing module did. I believe that the fan module is functioning properly and is not faulty.

[sunda]

Sorry, my reply was posted twice.

[sunda]

Thanks, Mig, for your cooperation.

Unfortunately, the table does not match my model, except for the first four connections to the Fan Control Module. Additionally, I could not locate the corresponding fuses in my diagram. However, the fact that the ECU triggers the fans via T4x/3, and that the high-pressure sensor sends a signal to the fan control module, provides useful clues for proceeding with troubleshooting.

I am unsure how to test the high-pressure sensor, so I will look it up online.

I connected a large fan that I purchased along with the module from the junkyard, and it behaves the same way as the existing module did. I believe that the fan module is functioning properly and is not faulty.

[ropak]

Hi sunda,

I'm interested to know if you were you able to solve the problem in the end. I'm having similar issues.

Thanks