Passat B6 radiator fans - which is which?

[DickBrowne]

hi all, I will ask the question first and then give some background, so if you don't want to plough through the dull stuff, you won't need to

I've got a 2006 B6 Passat 2.0 TDI Sport (140) and there are two fans on the radiator - a big one and a small one. Can anybody identify the purpose of each of these for me please?

The background is that I have a problem with my aircon - the fan blows fine but it doesn't get very cold. I had the AC recharged last year and it made a big difference. When this summer started it became obvious very quickly that I was once more suffering from a lack of cooling, so I headed back to the garage for a recharge and asked them to check the system for leaks. They reported that there was a minimal loss of refrigerant, well within what they would expect for a full year.

Whilst fiddling under the bonnet today, with the engine running, I noticed that there were two fans on the radiator. The big one was cutting in and out, which was what I expected it to do. The smaller one wasn't running at all.

A number of years ago I had a Rover 75 and it displayed similar symptoms - air con not cooling - there was a known fault with the 75 where the control module for the single radiator fan would fail and this stopped the fan turning, with the result that there was no aircon. I replaced the fan (which contained the module) and all was well.

I know that my model of Passat has a known problem with the air con compressor, but I'm hoping that the fix will be easier than this, and the smaller fan is linked with the aircon. I'm also hoping that a £3 part which takes six minutes to fix will do the trick, but then I'm an optimist

If anybody can confirm the function of the smaller fan and if it's failure will present the issue I have, I would be very grateful.

Many thanks

Richard

[martin1810]

Get a vcds scan done. That will tell you if the fans are ok.

[DickBrowne]

Get a vcds scan done. That will tell you if the fans are ok.

Thanks Martin - do you know if both fans are purely for engine cooling, or is there an aircon use also?

[RichardSEL]

Put Aircon on full (LO indicated on Climatronic control panel, dual off) immediately on starting engine.
Both fans should run

[DickBrowne]

Put Aircon on full (LO indicated on Climatronic control panel, dual off) immediately on starting engine.
Both fans should run

Thanks Richard, from my research that was what I had supposed to be the case, and it's good to have that confirmed. Only one fan is spinning up so I guess the question I know have is - will the small fan be not working because the air con isn't working properly, or is the air con not working properly because the fan isn't spinning?

Any help appreciated

[Teflon]

Thanks Richard, from my research that was what I had supposed to be the case, and it's good to have that confirmed. Only one fan is spinning up so I guess the question I know have is - will the small fan be not working because the air con isn't working properly, or is the air con not working properly because the fan isn't spinning?

Any help appreciated

You maybe need the aircon system checked for leaks/diagnosed. Just took the wife's car for an aircon service because it was dead; in the end it cost me £170 to replace a leaking G65 sensor.

[DickBrowne]

You maybe need the aircon system checked for leaks/diagnosed. Just took the wife's car for an aircon service because it was dead; in the end it cost me £170 to replace a leaking G65 sensor.

Hi Teflon - that was the first thing I did - I had a Volvo many years back with a leaking condensor, and it gave similar symptoms, needing a top-up every spring and losing efficiency toward the end of summer, failing to demist the windscreen effectively over winter etc. The good news is that coolant loss was within expected limits this year so we're pretty sure that the system isn't leaking.

I'm hoping the fan will prove to be the problem because it's relatively cheap (compared to the compressor) and I can do it myself rather than paying a garage for the work.

Richard

[RichardSEL]

There are some Climatronic diagnostics at: <just tried the link to my-gti.com and IE says site not found>
But I've never used them for the fault you describe
For more diagnostics for your specific query, as Martin has said, you'd need to have a scan done

I've got another .doc file of 50kB but apparently it's too "big" for an attachment -- very 80s!
<later> So it's only a .txt file now

[martin1810]

With aircon on it is quite normal for only the large fan to run. If you press econ on a basic model you can see the large fan slow and stop.

[DickBrowne]

Excellent - thank you for the codes. I popped the control panel into diagnostic mode last night but didn't have the codes with me to check (but at least I know I can get to the codes in my car ) - I shall take another look today.