Radiator Fan issue

[vegashc110]

2010 Octavia 140 bkd

 

So for a while I've noticed my radiator fan doesn't come on and yesterday replaced the coolant flange sensor switch (on the right of the head) to no avail. However when I disconnect this wiring the fan (larger)  starts and cycles fast and slow speeds. Connect the switch again and nothing happens (car had been out was hot/running and no kick in of the fan).

I have previously replaced the fans themselves. The smaller a/c fan hasn't run at all as far as I can tell. 

also where is the fan control unit located?

thanks in advance. 

 

[Breezy_Pete]

Perhaps the engine thermostat is stuck open, so there's always flow through the radiator, and the temperature just doesn't get high enough to trigger fan action? What does the gauge indicate?

(Unplugging the temp sensor in the head flange maybe puts the engine ECU into a 'overcautious' state with fan activity commanded?)

 

I don't have access to my circuits until this evening, but can have a look then. Fan control module I think may be integrated into the main fan unit.  Are there are any thin wires going to that?

[vegashc110]

I think the thermostat is okay. Temp gauge rises to 90 and never moves. Doesn't struggle to get there and never gone over. 

 

Yeah maybe when unplugged its like an overcautious state. At least I know fan works and power gets to it. It's why I was thinking control unit, hopefully an easy swap out fix.

 

I'll have a look at the wires soon and let you know. 

 

Thanks. 

[KenONeill]

@vegashc110 - Which actually proves that the engine coolant temperature is in the range of 70C to 105C. The instrument is programmed to read 90C (give or take) whenever the actual temperature Is in that range.

[vegashc110]

These photos are from the original fan that was on the car and is identical to what is on now. 

[nige8021]

It is the engine ECU, based on what temperature it is seing from the CTS that signals the fan control module to switch on the fan/s there is an overide from the radiator temp switch if this fails   

[Breezy_Pete]

The thin green wire is the one from the engine ECU, and it does confirm that the fan control module is built into the main fan unit.

 

It may be worth hooking up to VCDS to see what temperatures the coolant temperature sensor on the head flange is measuring.  That might help rule in/out my idea about the thermostat maybe not behaving itself.

 

Does the car have A/C? If so, do you get fan action soon after demanding cool air? That tends to be triggered by rise in refrigerant pressure, rather than coolant temperature, so should be effectively independent of anything the thermostat is/isn't doing. 

[vegashc110]

Cheers I'll have to check the temperature the sensor is picking up first. 

Car has a/c I don't get any fan action when switching on and the a/c isn't that cool but does de-mist on cold mornings albeit slower than it used to. Maybe needs a top up but I hadn't got around to it as I rarely use it. 

[vegashc110]

havent got access to vagcom but my old mpg reader shows coolant temp as 94-96 once warmed up and sat. Guess that rules out thermostat playing up?

20 hours ago, Wino said:

 

It may be worth hooking up to VCDS to see what temperatures the coolant temperature sensor on the head flange is measuring.  That might help rule in/out my idea about the thermostat maybe not behaving itself.

 

[KenONeill]

10 minutes ago, vegashc110 said:

my old mpg reader shows coolant temp as 94-96

Where does it get the data stream it's giving that value from?

[Breezy_Pete]

25 minutes ago, vegashc110 said:

havent got access to vagcom but my old mpg reader shows coolant temp as 94-96 once warmed up and sat. Guess that rules out thermostat playing up?

 

Yeah, I agree.

Not much left though if the fans have been replaced.  Were the replacement fans new?

[vegashc110]

15 hours ago, Wino said:

Were the replacement fans new?

They were off another car I stripped down for spares. They did work on the old car as normal.

 

[vegashc110]

16 hours ago, KenONeill said:

Where does it get the data stream it's giving that value from?

I'm unsure where the data comes from as it's a basic plug in tool and doesn't have anything in the manual. 

[KenONeill]

1 hour ago, vegashc110 said:

I'm unsure where the data comes from as it's a basic plug in tool and doesn't have anything in the manual. 

OK, so it doesn't actually prove that the CTS is good then, just confirms that the gauge is showing the value the CTS is feeding it.

[vegashc110]

3 hours ago, KenONeill said:

OK, so it doesn't actually prove that the CTS is good then, just confirms that the gauge is showing the value the CTS is feeding it.

Yeah. May not be the cts feed. But it's the second brand new one in 6 months so small chance I've had one break and two dud new ones (bought from eurocar parts and other from skoda). At least the feed I got rules out thermostat playing up. 

[vegashc110]

So got around to checking the CTS (thermostat side - switch side) with multimeter and got the following

 

Normal operation?, seems to lower as temp builds and once Thermostat opens ( cooler fluid from rad passes) shoots up then lowers again as temp rises through full system.

Car was just standing as i had multimeter plugged to sensor so couldn't drive it.

 

Next I went to see what power was going to fans

 

1. Earth

2. 12v battery

3.?

4.?

 

I'm guessing one of 3 and 4 is switch for Radiator fan and other is AC fan switch. I've googled a little but unable to find any wire schematics to confirm.

 

so the following shows what i got:

 

                IG off            IG on      IG+AC on

1+2            13v              14.2           14.2

1+3             0.33            14.2           14.1

1+4             0             0.08-0.30     0.1-0.30

 

Car was still warm from earlier (temp above 60°c but not at a temp to activate fans normally??) - AC in cabin doesnt cool at the moment so no change when switching between on/off!

between 1+4 meter showed a constant flux between those values??

 

Does this shed any light on where a problem might lie, Does anyone know what values we get in a normal operation when fans work correctly?

 

thanks in advance..

 

[Breezy_Pete]

So pin 1 is earth (brown wire?), pin 2 is permanent 12V (red wire?), pin 3 is an ignition on 12V (black?).

4 is a PWM signal from engine ECU which governs the speed of the fans, continuously variable. Green wire I think?

Nothing obviously wrong there but if engine was hotter I'd expect that voltage to go up and get the fans going; or if the AC was on and working.

[vegashc110]

5 hours ago, Wino said:

So pin 1 is earth (brown wire?), pin 2 is permanent 12V (red wire?), pin 3 is an ignition on 12V (black?).

4 is a PWM signal from engine ECU which governs the speed of the fans, continuously variable. Green wire I think?

Nothing obviously wrong there but if engine was hotter I'd expect that voltage to go up and get the fans going; or if the AC was on and working.

yeah thats correct colours and all seems to be right, think im going to bench test my spare fans and see what voltage will turn them on then get car upto good temp and see what mine is producing.

Thanks for the replies Wino