verrilli

I have a coolant system saga with my 2003 A4 quattro and I need some help with the end of the story (soon I hope)...
- It started with a coolant leak.
- Dealer replaced cooling sensor behind engine.
- Thermostat exploded - dealer replaced thermostat
- Thermostat leaked - dealer replaced thermostat again
- Fans stopped working - engine overheated - dealer wanted $1500 to replace fans and fan control unit
- I gave up with dealer and replaced the fans myself
- New fans would work until the engine heated up, then they would shut off and stay off
- I replaced the fan control unit
- Now the fans come on and seem work properly when the car is running. They only come on when radiator outlet temp gets above 35C or so. They also come on when the A/C is on. I can see proper operation on the VCDS.
- Problem is if the car is fully warmed up and after the car is shut off and then after about 15 minutes, the fans will come on full blast and drain the battery

I searched on the forums for similar problems. I found the issue with the water on relay 219 under the ECU. I opened mine up and there's no water there.
Also when the problem is occurring, pulling relay 219 doesn't stop the fans.

There are currently no fault codes with the engine.

What should I do next? I don't have a good wiring diagram or an explanation on how this system is supposed to work. Help would be appreciated.

Colin
Apex, NC

verrilli

some additional information...
I tested at J293 after the ign is turned off.
I get +12 from the thick red/blue wire.
The brown is ground
The signal wire is getting 5Hz, 11% duty cycle
The other thin wire is getting 12V

After the 15 minutes, the signal wire is getting DC @ 50mV
The other thin wire is at 0V

Should I be getting DC 50mV on the signal wire? Is that enough to make the fans come on high speed (since it's DC)?