Radiator fan not running

Snottie

Member
Hi, as the temperature starts to rise I have been looking to get my aircon going again, the radiator fan motor cable was knackered last year and after I fixed it and recharged the aircon it worked well. This year the fan does not run at all, with the engine at 90 and the aircon set at low the fan does not turn on. I swopped the fan and control unit with my other A2 and they worked no probs so for some reason the fan is not being asked to run
Any ideas? Don't have access to vcds until next week
 
Hi, as the temperature starts to rise I have been looking to get my aircon going again, the radiator fan motor cable was knackered last year and after I fixed it and recharged the aircon it worked well. This year the fan does not run at all, with the engine at 90 and the aircon set at low the fan does not turn on. I swopped the fan and control unit with my other A2 and they worked no probs so for some reason the fan is not being asked to run
Any ideas? Don't have access to vcds until next week

Perhaps your temperature sender is the problem?

It should be in the top hose somewhere? It is not the green one with 4 pins, that is used by the temp gauge and ECU.

If the Fan is working on the other A2 then the only thing you didn't swap over is the sender?

Steve B
 
Doesn't the fan run anyway with the A/C on, regardless of the engine temperature? If it doesn't run with the A/C on, it won't be the cooling system temperature sender. Fuse? Don't rely on the gauge giving you an accurate coolant temperature!

RAB
 
Radiator fan runs when A/C is in operation. Regardless of temperature.

Been down this road with my own car, and Timmus/Tom's assistance.

Snottie can you check your wiring again, sounds like that could be the issue or even the wiring and fuse? If memory serves me correctly I think the fuse for the radiator fan is a whopping great thing that's hidden behind the dash trim, above the location of the other fuses.
 
Ok so there is 12 volt going to the fan controller but only 4 volts going to the fan, even with the aircon on and the output test from vcds the output voltage to the fan does not change. Does anyone know where or what the control signal is. There are no fault codes for the hvac system either
 
Tom and I couldn't fathom the exact workings of the fan. It boggled our minds TBH. We couldn't find a control signal either!!!!

I know Tom/Timmus is a motivated fella, and electronics is his forté. He may well have discovered the workings by now. I'm unsure without speaking to him.
 
Ok it appears that the signals come from the aircon control panel, only when the engine temp is above 95 will the fan go to stage 1 then 102 it will go to stage 2, even today my engine sat at 90 so that's why it is not running when ticking over. It will not start when you turn on the aircon if the gas is not at pressure! It could simply be a low gas pressure then!

Does anyone have a wiring diagram / current flow diagram as audi call it!
 
Hi,

is that actual temperature or "gauge temperature"? The gauge reads a nice and sensible 90 degrees as the normal operating temperature, but it isn't, especially for the petrols and particularly the FSI. I guess 90 degrees sounds "safe" where as if it read for example 115 at the normal operating temperature people would get scared that the engine is overheating. That's why the engine water temperature sensor has two outputs and the ECU can loose the temperature signal from its half of the sensor even if the gauge seems to be working fine.

The climate control "D" connector pin 8 black/yellow goes to the fan controller pin 3 and climate control pin 9 yellow/grey goes to the fan controller pin 5.
These are the same pins on the fan controller as connected to the two stage thermostat in the radiator so I guess the climate unit can override the normal temperature control over the fan using the same inputs. The radiator thermostat works by connecting to earth to enable the fan so the climate unit probably does the same. You ought to be able to test the operation of the fan by connecting the inputs to earth yourself, although if the fan works, the climate unit my not be turning it on because it thinks something else isn't working properly.

regards

Andrew
 
Thanks Andrew, do you have a wiring diagram? The temperatures I quoted I got from an audi technical description, the car is a tdi, it sits at a constant 90 even in traffic in 30deg heat like today but still the fan does not kick in but the engine appears to not overheat.
I remember being able to display the actual engine temperature on the climate control so I will do it and watch what it sits at.

There is a 3rd core / pin in the control cable any idea what it is? Incidentally when I test the output through vcds the fan still does not operate so I think there is something really a miss. And before anyone asks yes there is 12 v going to the fan controller and yes I have tested the fan and controller in my other a2 and they work so issue is within the control signals only
 
Hi, I tried the test above and no joy, i grounded them at the fan to rule out bad cable and then belled the 2 cores out and they were fine through to plug d, pin 1 on the fan is blue, what is it? There is 1.2v on all 3 pins.
 
Hi,

the blue goes to the voltage regulator on the alternator. I guess its used to tell the fan controller when the engine is running. The same feed goes to the instrument cluster to make the no charge light come on if the alternator isn't working.

regards

Andrew
 
Cheers spike/ Steve totally missed that post! That's perfect, need to go digging but I think the problem is going to the the blue core going to the 6 pin plug it must supply 12 v when the engine is on and then the thermostats and aircon must switch the ground. However my test may have been a problem as I grounded pin 3 and 5 with the plug out so there was no 12 v,! Sure will give me something to do tonight when the kids are in bed!
Thanks for your help lads will keep you posted.
 
Mooohahahaha, That's it fixed, blue core going to the fan control box was broken just above the plug, looks like water got in, an aircon top up and it is as good as new.

Thanks everyone for you help, now all I need to fix is the faulty passenger door window switch and speaker, gearbox and engine mounts, sticking rear brakes and squealing front ones..... Bit like triggers brush!

To recap then, going to the fan controller 6 pin plug on pin 1 is 12v when the engine is running, pin 3 is then grounded by either the aircon control or engine thermostat, this sets the fan to run at stage 1. Then pin 5 is grounded as per pin 3 / stage 1 but at a higher aircon demand or higher engine temperature this sets the fan speed to stage 2. Thus if you put 12v to pin 1 and ground pin 3/5 the fan should run, proving the controller.
There is is a constant 12 v supply to the fan controller which is fed from a large fuse above the normal fuse box (requires lower dash removed to access)
The fan controller then takes the 12 v feed and sets the output to he fan at either none, stage 1 or stage 2 dependant on the input
Using vcds you can test the fan output but if your aircon pressure is low this will not work, thus the test fire is done through the hvac system and not the engine or instruments which I thought strange.
 
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I've got the same problem! Fan Control Module replaced with a known working unit. Has been an expensive year so far with preventative maintenance! ?‍♂️
 
Can't tell you how helpful this post was! An oldie but a goodie.
No gas resulted in the fan never going, which I thought was a controller issue, but when replaced, no change. The earthing of the pins resulted in rotation, and relief, after £30 wasted on a controller.

Now for gas, and hopefully more relief (in more ways than one!).

Great info and help, thanks to @Snottie and all those who post helpful info.
 
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