Weird radiator fan behaviour

[purdy1984]

Apologies in advance for lenghtly post but after hours of searching and reading I still can't pinpoint what I think must be a simple answer!
For months I've been trying to figure out my overheating issue and think I'm getting closer just not close enough to fix!
So when car gets to temp and stage one the larger fan comes on ( c.92 degrees) and sometimes the smaller fan. When the car gets to higher temp ( 99+ degrees) they dont switch to stage two and high speed to cool. If i turn car off they then both come on at high speed so the fans themselves work and spin freely. If i restart the car they will also then continue to run at high speed until the car is around 90 degrees.
Waterpump is fine and replaced recently and also change the coolant temp sender as part of trying to fix issue. All fuses are fine including the big 30 amp ones. All pipes are hot so believe thermostat is fine ( was also replaced a few years ago).
So why dont they come on when they should unless I turn ignition off and then back on when at temp? Any help greatly apprecited.

 

[MauriceT]

Maybe faulty cooling fan module?

 

[purdy1984]

As in the one in the big fan? I did wonder just confused as they work sometimes so thought they’d either work or not at all if that was faulty?

 

[Audi A3 S-Line 8p tdi]

Apologies in advance for lenghtly post but after hours of searching and reading I still can't pinpoint what I think must be a simple answer!
For months I've been trying to figure out my overheating issue and think I'm getting closer just not close enough to fix!
So when car gets to temp and stage one the larger fan comes on ( c.92 degrees) and sometimes the smaller fan. When the car gets to higher temp ( 99+ degrees) they dont switch to stage two and high speed to cool. If i turn car off they then both come on at high speed so the fans themselves work and spin freely. If i restart the car they will also then continue to run at high speed until the car is around 90 degrees.
Waterpump is fine and replaced recently and also change the coolant temp sender as part of trying to fix issue. All fuses are fine including the big 30 amp ones. All pipes are hot so believe thermostat is fine ( was also replaced a few years ago).
So why dont they come on when they should unless I turn ignition off and then back on when at temp? Any help greatly apprecited.

I've recently fixed my ongoing fan problem after about a year or more. So the first question is, what coolant temp sensor did you change and did it have any affect on the car?

 

[purdy1984]

I've recently fixed my ongoing fan problem after about a year or more. So the first question is, what coolant temp sensor did you change and did it have any affect on the car?

Change the grey/green one and no it’s made no difference so assume it wasn’t faulty

 

[NHN]

Depending on the engine, there could be 2 coolant senders.

Rad packs have been known to go faulty on 8P's also.