nemohm

I'm wondering if a malfunctioning cooling system would trow DTC?

- like failed radiator fan?

nemohm

What tests could pe be performed with a Vag-com targeting the coolant syatem?

aamakda

Hi,

sorry new here. The cooling fan in my audi A6 comes on during cold start, is this normal?

Please help

Thanks

K04-S4

Coolant Temp Sensor G2/G62 will typically trigger CEL and throw DTC's when failing. For the 2.7T and many other VAG engines it's a dual output sensor so the value sent to the Instrument Cluster may not be the same value that the ECU sees if it's failing. You can use VAG - Measuring Blocks to read coolant temp value and compare to dash gauge etc.

Cooling Fan operation can be checked with operating temp engine in warm weather. Fan and fan switch can be tested manually.

What specific issue is occuring?

nemohm

It looks like the 3 fans an Audi usually equipped with are more or less redundant.
-Viscous fan (belt driven)
-Radiator fan (V7)
-A/C fan (V177)

It appears to be very common to get rid of the viscous fan - S4 stage 2, 3 are running w/o it.
While doing TB I did not put that fan back.
V7 is not observed to engage.
Temperature needle stays in the middle (90 C) as cemented (while driving of course).
Looks like the thermostat does the major work here.
What would explain the 3 fans presence - uniform application for all climates?

Anybody from Arizona?

BTW-throughout the years Audi changed the cooling - A/C so many times from year to year - wiring diagrams as well, that IMHO general suggestions would be quite misleading.
Component location is very dynamic too…
No wonder there is a hardly any comprehensive description of the cooling - A/C function.
(Bentley is helpless).
Year and model specifics!!!



Looks like neither the radiator fan, nor the auxiliary (after run) water pump are functional.

The temperature gauge stays firm at 90C while the Vag-com reads 102C.

Following Bentley I opened the trim to look at the 8-fold relay panel fuses (under the left side of the dash) just to find out the panel is EMPTY!

Out of some 26 components described - I have 2 fuses only - 50 and 60? A.
Bentley has a clear photo with aux water pump located underneath, behind the oil pan=> the dealer confirmed the pump is between intake manifolds.
Now what?
Without any wiring docs it would be quite hard to diagnose the electrical issues.
Have to find another info source…..

Anybody with the exact same car?

Looks like the after-run-auxiliary-secondary water pump runs only if the coolant temperature is above 112 C (engine off).
Regulated directly from the ECM - no relays (Bentley involves 2 relays in the function).

Any confirmations?
Have you noticed your pump running?
(Must run simultaneously with the auxiliary radiator fan (V7).

CTS triggers code - but what about the rest of sensors- 2-pin Thermal switch and the 4-pin fan switch?

Have you test the HVAC with Vag-com - output tests?

(sorry for the long post)

K04-S4

If the CTS is giving different values between dash gauge and VAG then replace it as it's an inexpensive yet critical part. The black ones are the early bad design and Audi replaced them with improved green CTS.

After run pump for the 2.7T is supposed to run immediately after engine is shutdown.

Any sensor will trigger DTC for shorts or opens but may not trigger DTC if it is malfunctioning but staying within spec'd range limits.

nemohm

CTS was replaced under recall.
Secondary coolant pump gets triggered by 2-pin thermal switch (112C).

Why my 8-fold relay panel fuses has no components?
Is everything (low and hi speed relays) replaced by ECM's operations directly?

Have you test the HVAC with Vag-com - output tests?