Sudden high temperature without coolant loss, 1.4tdi

PlasticMac said:
This might not be, (probably isn't), practical, but you may be able to disconnect the fan from the FCM completely, and hard wire the fan to the fused side of the fan fuse, to give permanent running of the fan at high speed, and rule the fan speed in or out as the cause.
Would probably need to get the engine hot first, then run the fan.
Sounds a bit daft now I've written it ...
Mac.
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Would need to be a heavy gauge cable too.
Mac.
 
My first port of call would be to use diagnostic kit to activate the fans, this shows if the vehicle in its current state can opperate them or if their is a problem to investigate!
 
Thanks all. Hopefully the thermostat is actually o.k (it wasn't!!) ; when just started up the radiator pipes and radiator core are cold and remain so for a good long while even when the measured temperatures are 40-50 degrees however once the engine is up towards nearly 90 the upper radiator pipe warms up fully suggesting it is opening at the appropriate time.

I've carried on reading and using Google there are a few threads from here back in 2014 and onwards where some of the control logic is explained - seemingly signal from the climatronic unit contributes, and on the 6-pin connector, connection of pin 3 or pin 5 to earth are necessary to move the fan onto its higher power settings, and - as commented a couple of posts back - the fan control unit can have issues with water damage that can stop this happening. If I can open it up to look for damage, the "darlington transistors" can be replaced - as per posts from @RAB. I've got a replacement fan controller on the way from just round the corner from here for delivery Tuesday in case this makes a difference but will hold onto the removed controller to see if I can open it up now my curiosity is piqued.

Radiator cooling fan.

Hi all, Just had timing belts,pulleys,new water pump fitted etc, all fine but my mechanic informs me that the rad cooling fan is not working! although he says it spins freely by hand. My car is A2 1.4 petrol with AUA engine 2001 reg, what i need to know is the following; where is the...
www.a2oc.net www.a2oc.net

Main radiator Fan Manual Override?

I'm currently sitting at the foot of a large Hill with only one way over it and the Water temperature at 105 C and the gauge reading about the Same. Is there Any way to force the cooler Fan to come on manually without putting Further load on the engine or am I stuck waiting until it cools down...
www.a2oc.net www.a2oc.net

I'm going to clock off now, and raise an actual beer in everyone's direction. Cheers!
 
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Not read the above threads but certainly worth checking the radiator control fuse ABOVE the fuse box. It is an orange rectangle 40A fuse.

This I believe is the main power source for the fan controller mounted on the radiator.

Probably need to drop the drivers storage panel to access it.

You can bet if it has blown there is an issue with the fan controller itself. Also expect this fuse may be dealer only......
 
audifan said:
Not read the above threads but certainly worth checking the radiator control fuse ABOVE the fuse box. It is an orange rectangle 40A fuse.

This I believe is the main power source for the fan controller mounted on the radiator.

.... Also expect this fuse may be dealer only......
Click to expand...

Dealer only possibly if bought brand new - however, is this fuse a part that might be available through @A2Steve / @Clackers / @Ami ?

Would the fan run at all (ie, basic aircon-demanded speed that it does run currently) if this 40A fuse is blown though?
 
That depends if the fan controller is only responsible for speeds two and three, with the climate panel responsible for speed one. I have not been able to determine exactly the split / combination for the fan operation. Then the pressure in the climate system may also become a factor.


I would still hope that coolant temperature would not be be over ruled by a climate signal to prevent speeds two and three from operating.
 
The fan controller contains three Darlington transistors, possibly one for each fan speed. The lowest speed is (or should be) on with the A/C running, even with the engine cold. If it's not, either the A/C has failed or the controller has failed, which means that the A/C will not work either. Speeds 2 and 3 will be dependent on the output of the coolant sensor - not sure which one, but logically it would be the ECU one!

RAB
 
RAB said:
The fan controller contains three Darlington transistors, possibly one for each fan speed. The lowest speed is (or should be) on with the A/C running, even with the engine cold. If it's not, either the A/C has failed or the controller has failed, which means that the A/C will not work either. Speeds 2 and 3 will be dependent on the output of the coolant sensor - not sure which one, but logically it would be the ECU one!

RAB
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individual parts Audi A2 (A2) 2003 year Audi EUROPA 959050

individual parts Audi A2 (A2) 2003 year Audi EUROPA 959050 spare parts
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Based on the temperatures @audifan was quoting earlier and your observation above, from part 6 in the above diagram it would appear that the blue dual thermo sensor at the bottom of the radiator invokes the higher fan settings - although if I've not confused myself completely, the request for the fan speed increase is sent from the Climatronic unit to the fan controller but I've forgotten where I obtained this statement (it was here in A2oc somewhere but I can't find the thread).
 
Robin_Cox said:

individual parts Audi A2 (A2) 2003 year Audi EUROPA 959050

individual parts Audi A2 (A2) 2003 year Audi EUROPA 959050 spare parts
audi.7zap.com audi.7zap.com

Based on the temperatures @audifan was quoting earlier and your observation above, from part 6 in the above diagram it would appear that the blue dual thermo sensor at the bottom of the radiator invokes the higher fan settings
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Yes, that would make more sense, otherwise what is it for? Also I'm not sure it is at the bottom of the radiator.

RAB
 
Robin_Cox said:
the request for the fan speed increase is sent from the Climatronic unit to the fan controller but I've forgotten where I obtained this statement (it was here in A2oc somewhere but I can't find the thread).
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There should be no requirement for the Climatronic unit to increase fan speed; it only needs to run at the lowest speed for A/C.

RAB
 
RAB said:
Yes, that would make more sense, otherwise what is it for? Also I'm not sure it is at the bottom of the radiator.

RAB
Click to expand...
I've replaced one. It is at the bottom of the radiator in the pipe that runs to the thermostat housing, right next to the pump for the windscreen washer bottle if the undertray is absent.

See part 4 in situ.

coolant hoses and pipes; flange; reservoir Audi A2 (A2) 2003 year Audi EUROPA 121038

coolant hoses and pipes<br/>flange<br/>reservoir Audi A2 (A2) 2003 year Audi EUROPA 121038 spare parts
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audifan said:
Is the fuse blown?
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Don't know yet but going to get one from @Ami just in case. The fan runs in response to the basic a/c requirements, but I don't know if the 40A fuse would prevent this if blown (assume that the 350W fan requires nearly 30A for full power hence high rating of the fuse).

I do know that the fan controller connectors for all three plugs are in good condition with no evidence of corrosion on any of the pins, and I have been able to release them without destroying the connectors which is positive.
 
I think there are two circuits for the radiator fan. One for the climate cooling and probable the fuse INSIDE the fuse box, and the second for the coolant temperature overheat with its separate fuse ABOVE the fuse box. This is only my gut feeling but could easily explain why either the fan does not run slow for the climate or does not run faster to cool the radiator.

Certainly worth just having a check on the fuse.
 
I looked at circuits last night, and it looked like the dual thermal switch controls the two fan speeds, when AC is not fitted. Couldn't find it in the AC version circuit.
Mac.
 
PlasticMac said:
I looked at circuits last night, and it looked like the dual thermal switch controls the two fan speeds, when AC is not fitted. Couldn't find it in the AC version circuit.
Mac.
Click to expand...

individual parts Audi A2 (A2) 2003 year Audi EUROPA 959050

individual parts Audi A2 (A2) 2003 year Audi EUROPA 959050 spare parts
audi.7zap.com audi.7zap.com

this diagram suggests it is part 6 (8D0 959 481 B), for vehicles with a/c or conversely, also for vehicles with the 'warm climate' specification ; there is another part 6 (8D0 959 481) for vehicles without a/c. The non-ac cars also have a smaller diameter fan with lower power rating.

My other half's AUA has Climatronic a/c and the blue sensor was there ; I haven't got the undertray off mine yet but I anticipate the blue sensor will also be down there.
 
Found it, with AC, the dual thermal switch (F18 & F54) feed into the FCM.
1649693731763.png


1649693778903.png


Mac.
 
PlasticMac said:
Found it, with AC, the dual thermal switch (F18 & F54) feed into the FCM.
View attachment 93191

View attachment 93192

Mac.
Click to expand...
I must admit I have a very tenuous understanding of what any of this means above.

What I believe I do understand is that the F54 / F18 switches you've highlighted are the ones that connect pins 3 and 5 (presumably medium and high speed for the fan) of the 6-pin smaller connector to ground? And the E87 links to these two lines are signals from Climatronic but I don't know what this bit means and what it implies functionally.
 
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