2007 Audi S6 5.2 Overheating T/S

111F ambient the fans don't run from ECT alone. they run and ramp based on AC demand. VAGCOM Engine Output Test yields Both Fans work and ramp as requested by the VCDS program. So where the hell does the ECM get its engine temp from to run the fans? Is there some way to adjust at what temp the fans come on? is the 2 wire sensor in the Thermostat Housing the source for the ECM to measure the ECT and drive the fans? what is the second temperature value found in the freeze frame data (66.0C) below?


Address 01: Engine (4F1 910 552 A)

20:55:29 Group 004
640 /min RPM
12.596 V Voltage
96.0°C Temperature
66.0°C Temperature

Address 08: Auto HVAC (4F0 910 043 A)

20:35:34 Group 022: Radiator Fans
56.8 % Radiator Fans (V7) Request
66.0 % Radiator Fans (V7) Feedback
7.0 Air Quality Sensor (G238)
20.0 Fresh/Recirculated Air Request

20:35:34 Group 019: Temperatures III
34.0°C Dash Panel (G56) Temperature
2760 /min Temp. Sensor Blower Speed
94.0°C Coolant Temperature
ON Idle Speed Increase Request

That 5.2 is a V10, right? If so, it has not just one but two ECMs, and in all likelihood, a small plethora of temperature sensors.

-Uwe-

yes V10, and yes 2 ECMs, I do have a code for one of them. what is the second temperature reported? is there a adaptation for turning on the fans? calibrating the Temp Sensors? where can I find what the ECMs use to control the FCMs? Is the 2 wires going into the Thermostat Housing a Thermostat for Mapped Control Cooling?

http://www.vaglinks.com/vaglinks_com/Docs/SSP/VWUSA.COM_SSP_923603_5.2lL_V10_FSI_Engine.pdf

006435 - Please Check DTC Memory of ECU Number 2
P1923 - 008 -
Freeze Frame:
Fault Status: 01101000
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 191228 km
Time Indication: 0
Date: 2020.08.06
Time: 20:42:25

Freeze Frame:
RPM: 0 /min
Load: 0.0 %
Speed: 0.0 km/h
Temperature: 95.0°C
Temperature: 60.0°C
Absolute Pres.: 950.0 mbar
Voltage: 11.938 V

CBR900RRR said:

what is the second temperature reported?

Click to expand...

Unfortunately, with freeze-frame data, what you see is what you get, and I have no way to know.

CBR900RRR said:

is there a adaptation for turning on the fans? calibrating the Temp Sensors?

Click to expand...

I've never seen such a thing in any ECU and wouldn't expect to find it in yours either.

CBR900RRR said:

iwhere can I find what the ECMs use to control the FCMs?

Click to expand...

Wiring diagrams for your specific car? The SSP for the V10 engine?

-Uwe-

Love your signature, nice to see another Red Piller. updated my link to the 5.2 and its pretty clear G62 and a mapped control coolant thermostat are used. I failed to realize engine temps can go up to 105C. assumed 100C was bad. I've replaced the pressure cap and haven't seen a boil-over in any of my testing since, maybe I don't have an issue anymore and need to just drive it. fingers crossed, I appreciate your feedback.

Hi there...

Just to let you know, we did receive your Auto-Scan in your email to Ross-Tech support for the 2007 A6.
If you need more help on the forum, it would be a good idea to post the complete vehicle Auto-Scan.

As far as coolant temps, 105°C is plausible and if needed here is a link for the Official Factory Repair Information.


Hope this helps,

drpeter

I only have high-end motorcycles for detailed reference, but principle is the same so here goes:

While driving highway speeds, 75-85º is normal, standing still fans usually cut in at 105º. The system is pressurized so 100ºC is not the boiling point. Usually temperature warnings trigger around 120-125ºC, boiling point with a normal 1.5 bar overpressure in the system (this one can differ, i'm not sure what the nominal overpressure is in a car cooling system) will be around 130ºC.

In cars, you will never see the coolant temp gauge move from 90ºC, but in motorcycles you will get an actual reading which will go down rapidly when driving, and go up rapidly when standing still until the fans come on at 105ºC.

MasterTommy said:

In cars, you will never see the coolant temp gauge move from 90ºC,

Click to expand...

Yep, it shouldn't move in VAG cars; they've had "liar" coolant temperature gauges for decades (since at least the Mk3 generation). Those gauges are basically a three-position indicator: 1) Cold, 2) OK, and 3) So hot you'd better do something about it immediately. I guess they got tired of owners complaining that the temperatures shown by the gauge fluctuated or were "too hot". I agree; 105ºC is not too hot for a pressurized cooling system that's running a proper mixture of glycol and water.

If someone wants to see the actual coolant temperature, it's available in the measuring values in the engine and the instrument cluster with a scan tool. Yes, it fluctuates with engine load, vehicle speed, and other factors.

-Uwe-