Low speed fans for AC and high speed fans for engine cooling use relays in the fan control module.
So your issue could point to that.

Low speed fans for engine cooling are just a basic permanently live circuit, no relays involved.

FYI "Econ" on means AC off.
You need the Econ light off to have the fans running all the time.

 

Hi, High speed fans are controlled by thermal switch via the Fan control module.
Hoggy.

 

Hi, High speed fans are controlled by thermal switch via the Fan control module.
Hoggy.

So if the module is faulty the fans won't work When bridged across the thermal switch plug ? As the low speed did which isn't controlled by it?

Low speed fans for AC and high speed fans for engine cooling use relays in the fan control module.
So your issue could point to that.

Low speed fans for engine cooling are just a basic permanently live circuit, no relays involved.

FYI "Econ" on means AC off.
You need the Econ light off to have the fans running all the time.

Sorry that's correct I got that mixed up. It's not running at all with it off.

I presume it has a faulty thermal switch and module then... bugger.

 

As above plus the fuses on top of the battery can be sneaky buggers they must be a very tight fit and it's worth checking the underneath of them for any burning and corrosion so turn the unit over to see.

Stevie

 

Put a new thermal switch on to see if low speed would work, no low speed at all. Rechecked fuses. All ok power to them on the contacts.
Tried removing fuse 16 as somewhere on the forum it said this would cause them to run, still nothing.

 

Put a new thermal switch on to see if low speed would work, no low speed at all. Rechecked fuses. All ok power to them on the contacts.
Tried removing fuse 16 as somewhere on the forum it said this would cause them to run, still nothing.

Remember, two methods used to turn on the low speed fans.
For engine cooling it is just the 1st stage of the 2-stage thermal switch on the rad.
For the AC it is a relay in the fan control module.

Both methods use the green 30A fuse for the supply.

 

Remember, two methods used to turn on the low speed fans.
For engine cooling it is just the 1st stage of the 2-stage thermal switch on the rad.
For the AC it is a relay in the fan control module.

Both methods use the green 30A fuse for the supply.

I thought the low speed bypassed the fan control module so would work with ac..
tried with exon off and still nothing. I will try a new control module, hopefully here on Thursday.

 

Hi, The low speed fans for coolant temp control, byepass the FCM. High speed for coolant temp control use the FCM
Low speed for A/C use the FCM.
Nothing simple on the TT..Vorsprung durch Technik :roll:
Hoggy.

 

Sorry, but another variable is I don't think the low speed fans will run if there is not enough refrigerant/pressure in the a/c, but should still run if the rad temp switch demands.

this may be helpful...

 

Found the cause. On the plug connector to the FCM. Wiring repair carried out start up. Fans running low speed, now to road test and see if high speed operate.

 

Found the cause. On the plug connector to the FCM. Wiring repair carried out start up. Fans running low speed, now to road test and see if high speed operate.

Good man! [smiley=cheers.gif] [smiley=thumbsup.gif]

 

Well...

High speed fan isn't coming on. Have to turn car off and back on so still getting to 130.. low speed is working fine, am I to try a different FCM? Does this sound like the problem ? Possibly been sent a faulty one?

So making progress just not solved. Cheers for the help so far guys.

 

Hi, With a coolant temp of 130 I would expect to see steam issuing from reservoir vent if 130 is true temp.
Hoggy.

 

Hi, With a coolant temp of 130 I would expect to see steam issuing from reservoir vent if 130 is true temp.
Hoggy.

I expected this myself so swapped coolant temp sensor and still nothing. Unsure as to why it's happening. Possibly wrong reading from somewhere.

 

Spoke to my dad. He said that the dash is reading 70C in the morning. So may be the dash pod I now presume. The joys.

 

Spoke to my dad. He said that the dash is reading 70C in the morning. So may be the dash pod I now presume. The joys.

Hi, Are you using Code 49 on climate control for coolant temp indication? Click link.

High speed fans should be running by 106 ish
Hoggy.

 

Hi All,

I've got a similar problem with my 04 3.2, it started in the warm weather recently, temp gauge went upto 120c, upon investigation only the small fan was working, so replaced both fans & both radiators as they looked a bit dodgy & had it regassed.
I ran up to temp with diagnostic tool keeping exact eye on the temp, at 110c the fans worked & switched off less the 30s later, temp is now 108c, so thought everything was sorted.
On the recent warm day 28/29c ambient temp, the temp reached 120c, I pulled over & no fans are running
Did a bit of youtube research & suspected fan controller to be faulty, so changed that as well as radiator sensor, ran it last night & fans came on at 110c, but drove home & temp went high again 120c, no fans running, wtf
Any ideas?
Btw would VAG com be able to individually test circuits or does it only read errors?, thinking of getting it

Also the aircon pump clicks after switching off, could this be connected?

 

Hi All,

I've got a similar problem with my 04 3.2, it started in the warm weather recently, temp gauge went upto 120c, upon investigation only the small fan was working, so replaced both fans & both radiators as they looked a bit dodgy & had it regassed.
I ran up to temp with diagnostic tool keeping exact eye on the temp, at 110c the fans worked & switched off less the 30s later, temp is now 108c, so thought everything was sorted.
On the recent warm day 28/29c ambient temp, the temp reached 120c, I pulled over & no fans are running
Did a bit of youtube research & suspected fan controller to be faulty, so changed that as well as radiator sensor, ran it last night & fans came on at 110c, but drove home & temp went high again 120c, no fans running, wtf
Any ideas?
Btw would VAG com be able to individually test circuits or does it only read errors?, thinking of getting it

Also the aircon pump clicks after switching off, could this be connected?

Those temperatures are far too high. Fans should be running long before 110degC. That in itself points to the Low Speed fans not working so you're getting no fans at all until it is hot enough to trigger the High Speed Fans, then when it has cooled enough to go back to Low Speed fans they stop because Low Speed isn't working.

Do both fans run CONSTANTLY when the AC is on?
They should be running all the time at low speed for the AC.

I don't think VCDS can't trigger the fans because they are controlled by thermal switches, not the ECU via sensors.

Were your replacement fans new or secondhand?

 

Hi Max, What are you using to monitor the coolant temps, is it Code 49 on Climate Control?

Are you sure those temps are correct & not false high indications?
Replace Coolant temp sensor & use OEM.
Hoggy.

 

Both fans are new & I checked both speeds before fitting.
They both run when the AC is on, but AC is not working, but regassed & passed 20 min vauum test, which would also confirm high pressure ac sensor is working, mag clutch operates.
The temp gauge reads 90c, but reading on G62 code, coolant temp is 90c +, at 110c fans come for 30s & switch on/off 108-110c, but once above that, they won't switch on it seems.
After replacing cooling control module & rad sensor I have the same problem as previous, so assume it's something else?
I beleive the thermostats or temp sensors for the dash gauge is not linear, but staged, so temp range on 90c can actually be from 90-118 as "normal", after 118 the gauge rises.

 

Hi, Dash gauge is weighted & will read 90 when actual coolant temp on Code 49 is anywhere between 82 & 106 ish.
As you know fans are controlled via thermal switch & FCM, any coolant temp indications are just that an indication, so wondering are the temp indications showing a false high.
If replacing coolant temp sensor always use OEM. not OEM quality from Ebay etc.
Hoggy.

 

Get to the connector for the thermal switch on the rad and with the ignition OFF short pins to trigger the low speed fans.
If that doesn't work there is a wiring issue.

If that does work, then it could be a false high from a dodgy temperature sensor or faulty dash.

 

Hi, It's surprising how many have chased fan probs to eventually find the coolant indication was a false high.
Nothing simple on the TT....Vorsprung durch Technik
Hoggy.

 

Hold your horses Hoggy
I have checked the plug lead from the rad sensor, bridged the connection & the fans spin up.
I've also got coolant reading via the air con display see picture, it did actually get 116c with no fans running, I can bring it back down by switching AC on, therefore engaging low speed fans.

 

Hi Max, Replace coolant temp sensor & as I stated earlier use OEM & not OEM "quality". Fairly cheap & easy.
Hoggy.