Hello everyone,

I have a Octavia Scout 2007 BMM engine that has a new compressor, G65 sensor, condenser and expansion valve. Today it was in for a vacuum and regas. The garage told me it was blowing cold air for 10 seconds and then no more. The condenser gets extremely hot and the fans are not turning on. The fans did however turn on and the AC worked fine when they forced the fans to run via diagnostic equipment.

They did find the fault code P01274 - but they dont know of this is related to the Condenser Fan(s) not turning on.

They suggested I could maybe wire in a switch to manually turn on the condenser fans to get the AC working, but I'd rather find out what is wrong, and I'm not even sure this would work.

Some history:
I have also seen the fans running after I changed the high pressure N65 sensor and regulating valve on the old compressor and recharged the system with a DIY gas. This was in a cool evening, and the AC worked. The day after, when it was pretty warm outside, the fans did not run and the compressor pressure relief valve blew. It gets very hot and high pressure when the fans are not running.

After this I decided to replace the compressor, condenser and expansion valve because I thought there was something wrong with the pressure not engaging the fans via the N65 sensor, but it seems like the fan operation is the problem, or atleast part of it.

After a lot of stupid decisions (should have gone straight to a dealer with proper AC gauges and diagnostic equipment first) I now believe something is wrong with either the fans or the electrical system before the fans.

I am posting here while still having troubleshooting left to do - but with limited time available before a road trip through Europe I decided to post here and see if someone can point me the right direction.

 

Grateful for any comments or replies. 

 

Regards, U 

 

I have the double fan setup where the Fan Control module is integrated in the main fan J7. The smaller fan is a slave off the main fan J35.
 

Anyone know if the Fan Control Module or  one of the fans could be faulty even if the fans are operable if they are forced on via diagnostics? 

 

The fans and the fan shroud is similar to this:

https://m.autodoc.co.uk/tyc/7489544

Is the G65 pressure sensor accessible enough to inspect the condition of the connector and wiring near it?

 

As far as I can see, the fan set-up has a permanent 12V feed, an 'engine running' 12V feed, an earth, and a signal/control wire from the engine ECU.

If this signal wire is able to cause fan action via the diagnostics, it seems to me that the sensing of refrigerant pressure may be the area where the problem lies, and incorrect information about that pressure is leading to inactivity of the fans. 

 

The data signal from G65 is read by the HVAC module, and presumably that communicates by CAN with the engine ECU to say "pressure of refrigerant is too high, please operate the radiator fans".

 

Some monitoring of measuring blocks in HVAC and engine modules may be required to see where the info is/isn't getting to.

 

When activating radiator fans via diagnostics, is that by addressing the engine ECU, or the HVAC module?  It may be possible to do it via either, in which case, try the other one.

 

 

 

Edited 19 August, 20214 yr by Wino

Thank you for the reply, Wino. 

 

My research has shown the same description of the system as you describe. This is why I thought something was wrong with the pressure earlier, but seems like it is something wrong about the information about pressure as you say. 

 

Do you have access to a wiring diagram? I think I have seen one you posted in another thread. 

 

The wiring to the G65 sensor is accessible, so I will check that out. Could even try the old G65 sensor... 

 

I need to get my hands on VCDS to do the monitoring you mention. Deep regrets for not ordering Ross-Tech equipment a few months ago now. 

 

I'm not sure which module the garage used to activate the radiator fans, but I have been thinking the same. 

 

 

Also: Both shops (The one that did the regas and another VAG garage on the phone) I have been talking to has generally suggested there may be a sensor, or temperature sensor messing about... (Lots of help)

Wiring diagrams are available to anyone for a small fee, at erWin Skoda.  7 euros plus tax for 1 hour of downloading.  

I try not to post anything that isn't already 'wild' on the web, as they are all copyright documents.

I'll do that! 

PM me if you need any help finding what you need.

 

The engine output test is able to start the radiator fan. 

 

Reading the measuring blocks in the HVAC module everything seems fine, and it tells the radiator fan to go at a speed between 0 and 100%. I only tested it up to about 70% because I didnt wanna run the compressor and condenser too hot. 

 

Could it be that the output test is 100% fan speed, and bypasses the fan control module? 

 

See attached pdf files. See the errors related to the fan control module.

aUTO SCAN.pdf engine codes.pdf

Not sure TBH, and just off out so no time to ponder it just now.

I think everything has to go via the fan control module, whatever is demanded, but will revisit later on.

 

Crazy as it is, the guy I rented the RossTech from had a new complete fan assembly in his garage. I bought it. I am going to try and swap it out. 

 

Here are the error codes related to the coolant fan control

 

005746 - Coolant Fan Control 1 
 P1672 - 000 - Open or Short to Ground - Intermittent
 Freeze Frame:
 Fault Status: 00100000
 Fault Priority: 3
 Fault Frequency: 71
 Reset counter: 255
 Mileage: 240260 km
 Time Indication: 0
 Date: 2000.00.00
 Time: 16:59:51
 Freeze Frame:
 RPM: 1197 /min
 Speed: 62.0 km/h
 Load: 29.4 %
 Voltage: 14.52 V
 Bin. Bits: 00101000
 Temperature: 80.1°C
 Duty Cycle: 9.7 %

006469 - Control Module 1 for Cooling Fan
 P1945 - 000 - Output Short Circuit - Intermittent
 Freeze Frame:
 Fault Status: 00100000
 Fault Priority: 3
 Fault Frequency: 1
 Reset counter: 255
 Mileage: 240275 km
 Time Indication: 0
 Date: 2000.00.00
 Time: 10:50:02
 Freeze Frame:
 RPM: 819 /min
 Speed: 0.0 km/h
 Load: 0.0 %
 Voltage: 13.98 V
 Bin. Bits: 00101000
 Temperature: 54.9°C
 Duty Cycle: 9.7 %

006470 - Control Module 1 for Coolant Fan
 P1946 - 000 - Defective - Intermittent
 Freeze Frame:
 Fault Status: 00100000
 Fault Priority: 3
 Fault Frequency: 8
 Reset counter: 255
 Mileage: 240301 km
 Time Indication: 0
 Date: 2000.00.00

Freeze Frame:
 RPM: 1659 /min
 Speed: 87.0 km/h
 Load: 10.2 %
 Voltage: 14.44 V
 Bin. Bits: 00101000
 Temperature: 77.4°C
 Duty Cycle: 9.7 %

Solved 

 

New fan assembly with both fans did the trick. I think the main fan with the integrated fan control module was the fix.