Where is the thremo relay switch located on a 2003 3.0 audi A4. my problem is the radiator fans won't shut off and have been told this may be the problem

replace thermo switch... this is normally located near radiator hoses.

Hi,To fix the problem you have to replace the fan relay and/or temp switch. Good luck.

either the relay to the fan motor might have malfunctioned, or else the thermostat switch would not be working. have these two checked first.

if you find both of them working properly, direct the fan to the battary terminal and have the fan motor checked.

SOUND LIKE FAULTY CLUTCH FAN OR THE AUXILIARY ELECTRIC COOLANT FAN NOT RUNNING. CHECK AUXILIARY FAN FUSE AND RELAY. IF LOOK GOOD HOT WIRE TO SEE IF FAN TURNS ON IF NOT FAN FAULTY. IF FAN RUNS YOU HAVE FAULTY THERMO SWITCH. WHICH LOCATED AT THE BOTTOM OF RADIATOR ON THE LEFT HAND SIDE OR ON THE LOWER RADIATOR HOSE ON THE RIGHT HAND SIDE OF THE ENGINE COMPARTMENT.IF FANS OKAY COOLANT LEVEL CORRECT.REPLACE THERMOSTAT.HAVE RADIATOR AND ENGINE FLUSHED.CHECK IN FRONT OF GRILLE MAKE SURE NO DEBRIS BLOCKING OFF AIR FLOW THROUGH RADIATOR CORES AND AC CONDENSOR CORES.

it may be in the fuse box it might look like a little box shape about 1" square that pulls out of the fuse box ......cheers

The only place to get a wiper relay is from an Audi dealer. However, I have that same problem and the relay didn't fix it, I'm still trying to figure it out. I would try the relay first though, it's about $60 I think.

What does the fan do when you restsrt/charge the battery? Start up again? Replace the sending unit, or unplug the sending unit first. If fan keeps running, the relay is faulty.
if it stops, the sending unit is at faulat. good luck

One of those fans may only be powered during AC operation, the other should be controlled by a thermostatic switch often mounted on the bottom tank of the radiator and may not employ a relay at all. 

it could be a faulty fan switch, or faulty engine coolant temp sensor or a faulty fan relay