when does the radiator fan turn on while idling?

[Nobodyman]

My audi's temp stops at 93C and goes down to 91 and back to 93 while idleing and the fan never turns on. I'm afriad maybe my temp sensor is not working or something

I tested my fans through vcds on a sequence and they both worked but i havent actually seen they turn on other than that time.

Do they only run when the car is driving? with constant rpms? i find it hard to believe a v8 and can cool itself just on the water pump itself.

also when the car reaches 93C the temp needle at the dashboard turns off randomly. I can turn it back on when i change the dashboard lights, but then it starts to dim and flicker randomly

[LightningLou]

You said a v8? Are you talking about your s5 or a b5 s4 with a v8 swap? Not sure if you accidentally posted here or not... But, If the fan is working in vcds you should be good. Does the fan turn on when you switch on the a/c?

[zillarob]

If a 2.7, wonder if you have a 92deg tstat?

[Nobodyman]

You said a v8? Are you talking about your s5 or a b5 s4 with a v8 swap? Not sure if you accidentally posted here or not... But, If the fan is working in vcds you should be good. Does the fan turn on when you switch on the a/c?

ac gas was released, but i plugged in the sensor. Either way i can not turn the ac on, the button turns on and off right away.

yes its a s5, but the s5 forums don't reach a majority amount of people, or atleast i dont get the answers i need. But this is a radiator fan problem. older s4s were v8 as well so i decided to post here

[Nobodyman]

here was a live data readiness when i turned the engine on

[zillarob]

Wouldnt surprise me if it had some goofy elect tstat and that is just the way it works.

[Nobodyman]

101C and no fan turned on\

[ElementR]

I don't know specifics on your system but I develop powertrain cooling systems for a living so will tell you that there are only a few things that signal the PCM to command fan: TWT (top water temp, i.e., the temp of coolant coming out of the engine heading into your radiator), TOT (trans oil temp, typically only for automatic cars), EOT (engine oil temp) and A/C head pressure.

An engine functions most efficiently around 80-90 C. The thermostat will keep all the heat in the engine (of course with some going to the heater core and in some cases a trans cooler or emissions devices) until around 80-90 C depending on the engine and application. At that point, the t-stat will open allowing coolant to flow through the radiator to maintain coolant temperature as close to intent as possible... largely based on max engine efficiency goals. The cooling fans are normally triggered as coolant temps start creeping upwards of 100 C, but are calibrated based on the OEM's goals so you could see fans switch on as the low 90 C range or as high as say 100 C.

Based on your first post I would say this may be normal for your car, but if you are not seeing the fans switch on by 101 C, I would suspect an issue likely with the cooling fan module itself or with wiring leading to it. First thing to try is to switch the A/C on and see if the fan turns on but I see that you mentioned your A/C does not work. So, I would first check to see if you have a blown fuse for the fan. If not... Given that it's an Audi, and a 2010 S5 at that... your fan module is almost certainly variable speed. Instead of the standard low and high speed, the fan module can operate from zero to max speed or pretty much anywhere in between depending on the control strategy. There's typically three wires going to it... power, ground and control signal. The latter is the thinnest wire. If you have an scope or a meter capable of reading a PWM signal, you could check to see if it is being commanded. I'm not sure if your fan module is set to default to 100% speed if the control line is pulled low (i.e., grounded) or left open circuit. A trick to trigger the fan to turn on in absence of a signal from the PCM is to ground it or open the circuit. However, my money is on the fan module being bad before the control signal being absent.

If you rule out the fuse, I suggest checking the fan module next.

[Nobodyman]

I don't know specifics on your system but I develop powertrain cooling systems for a living so will tell you that there are only a few things that signal the PCM to command fan: TWT (top water temp, i.e., the temp of coolant coming out of the engine heading into your radiator), TOT (trans oil temp, typically only for automatic cars), EOT (engine oil temp) and A/C head pressure.

An engine functions most efficiently around 80-90 C. The thermostat will keep all the heat in the engine (of course with some going to the heater core and in some cases a trans cooler or emissions devices) until around 80-90 C depending on the engine and application. At that point, the t-stat will open allowing coolant to flow through the radiator to maintain coolant temperature as close to intent as possible... largely based on max engine efficiency goals. The cooling fans are normally triggered as coolant temps start creeping upwards of 100 C, but are calibrated based on the OEM's goals so you could see fans switch on as the low 90 C range or as high as say 100 C.

Based on your first post I would say this may be normal for your car, but if you are not seeing the fans switch on by 101 C, I would suspect an issue likely with the cooling fan module itself or with wiring leading to it. First thing to try is to switch the A/C on and see if the fan turns on but I see that you mentioned your A/C does not work. So, I would first check to see if you have a blown fuse for the fan. If not... Given that it's an Audi, and a 2010 S5 at that... your fan module is almost certainly variable speed. Instead of the standard low and high speed, the fan module can operate from zero to max speed or pretty much anywhere in between depending on the control strategy. There's typically three wires going to it... power, ground and control signal. The latter is the thinnest wire. If you have an scope or a meter capable of reading a PWM signal, you could check to see if it is being commanded. I'm not sure if your fan module is set to default to 100% speed if the control line is pulled low (i.e., grounded) or left open circuit. A trick to trigger the fan to turn on in absence of a signal from the PCM is to ground it or open the circuit. However, my money is on the fan module being bad before the control signal being absent.

If you rule out the fuse, I suggest checking the fan module next.

I was sure i checked every fuse i could find in the car and check if it was blown. I'll check the fuses again, it could be the module. What i did was buy a new fan shroud(support) and just put the old fans and module onto the new plastic support. I tested the fans in the sequence and like i said, it went from 0%-100% "duty". It instantly started turning at 5% and got faster and faster within 10 seconds. So since the motor was working i figured the module was working too

Here is my fault codes in my engine module BTW: its an old battery that had cells replenished recently. Thats the low voltage fault i assume

Address 01: Engine (J623-CAUB) Labels: 079-907-560-CAU.clb
Part No SW: 8T0 907 560 T HW: 8T0 907 560
Component: 4.2l V8/4V H10 0004
Revision: 76H10---
Coding: 01140009190F0120
Shop #: WSC 41580 000 1048576
VCID: 4B9548F3EA83B579CA9-801E

5 Faults Found:
005715 - Please check DTC Memory of ABS Controller
P1653 - 001 -
Freeze Frame:
Fault Status: 01100001
Fault Priority: 2
Fault Frequency: 18
Reset counter: 255
Mileage: 0 km
Time Indication: 0

Freeze Frame:
RPM: 0 /min
Load: 0.0 %
Speed: 0.0 km/h
Temperature: 1.0°C
Temperature: 4.0°C
Absolute Pres.: 0.0 mbar
Voltage: 0.000 V

005715 - Please check DTC Memory of ABS Controller
P1653 - 008 -
Freeze Frame:
Fault Status: 01101000
Fault Priority: 2
Fault Frequency: 25
Reset counter: 255
Mileage: 0 km
Time Indication: 0

Freeze Frame:
RPM: 0 /min
Load: 0.0 %
Speed: 0.0 km/h
Temperature: 1.0°C
Temperature: 4.0°C
Absolute Pres.: 0.0 mbar
Voltage: 0.000 V

006473 - Control Module 2 for Coolant Fan
P1949 - 008 - Defective - Intermittent
Freeze Frame:
Fault Status: 00101000
Fault Priority: 2
Fault Frequency: 1
Reset counter: 255
Mileage: 64946 km
Time Indication: 0
Date: 2009.05.20
Time: 19:27:20

Freeze Frame:
RPM: 0 /min
Load: 0.0 %
Speed: 0.0 km/h
Temperature: 4.0°C
Temperature: 12.0°C
Absolute Pres.: 990.0 mbar
Voltage: 11.684 V

005388 - RPM Request from Transmission
P150C - 004 - Cannot be Performed - Intermittent
Freeze Frame:
Fault Status: 00100100
Fault Priority: 2
Fault Frequency: 1
Reset counter: 255
Mileage: 64946 km
Time Indication: 0
Date: 2009.05.20
Time: 21:38:09

Freeze Frame:
RPM: 0 /min
Load: 0.0 %
Speed: 0.0 km/h
Temperature: 10.0°C
Temperature: 16.0°C
Absolute Pres.: 950.0 mbar
Voltage: 6.731 V

005634 - Power Supply Terminal 30
P1602 - 002 - Voltage too Low - Intermittent
Freeze Frame:
Fault Status: 00100010
Fault Priority: 2
Fault Frequency: 1
Reset counter: 255
Mileage: 0 km
Time Indication: 0

Freeze Frame:
RPM: 0 /min
Load: 0.0 %
Speed: 0.0 km/h
Temperature: -40.0°C
Temperature: -40.0°C
Absolute Pres.: 0.0 mbar
Voltage: 0.000 V

Readiness: 0110 1101

[ElementR]

Sorry - I missed your comment about having already tested the fans. Your code above says defective fan control module. I'm not sure if you have the type of fan module with integrated controller right into the back of the motor(s) or the kind that is remote mounted typically close to the motor and right on the fan shroud. I have seem the control modules remote mounted elsewhere in vehicle but that is rare are they are usually supplied by the maker of the fan and motor/shroud assembly and as such together as a system. So, if your module is defective, the whole fan module would need to be replaced unless they have a service part for the module itself (atypical). The intermittent fault code makes sense though based on what you're experiencing. Make sure the air path is not blocked in any way to the fan or around the motor and controller. Also make sure no objects are stuck in the fan. If that comes back clean, you likely have a defective fan assembly.