I hope someone can help.

 

My wifes A3 has been running a little hot for a while now. This weekend I changed the thermostat and temperature sender.

 

It seems to run happily at 90 for a while then the temperature rises to 110 or so.

 

When I was fiddling on it I noticed only 1 of the 2 rad fans was spinning, should both spin?

 

Waterpump?

 

Any help appreciated.

 

Thanks.

Both should spin, common for the first speed to fail, see here and the links within.

Which fan is working, the smaller or the larger?

I cant remember whish is bigger than the other, but the passenger one isnt working. Although it spins freely by hand.

Sounds like the same failure to me.  You can test by unplugging at the three-way connection low down on the back of the fan shroud and measuring resistance at the fan connector, I bet you'll find very high resistance between the brown wire and the one next to it, indicating that the internal low-speed resistor is no longer working.  Check fuses as well, probably in holder on battery.

See how many wires you have going to the other (working) fan while you're there. On some VW and Skoda models (one of each, 2003 and 2005 respectively) I've found that the smaller fan that blows at the A/C compressor and alternator is only single-speed, despite the wiring in the loom up to its three-way connector having all three wires. I think on earlier cars it was two-speed/three-wire like the main passenger-side one.

 

What year's this car?

Edited 6 July, 201610 yr by Wino

I will take a look thanks.

 

Its a 2003, 8l A3, late model close to the Mk2 being released. In fact some components on this model are from the MK2 I have found.

Switch on the A/C after it's fully warmed up and see if the main passenger-side fan cycles in and out of high speed after it's sat a while.  From what I've read, if the low speed fails, it can cause the 40A fuse for the high speed to fail after a while because the surge current is that much higher if it has to start up from stationary rather than just accelerate from the first speed.  On Polo and Fabia from the same era, the low speed fans work off a 30A blade fuse (under a cover) and the high speed off a 40A strip-fuse, both on top of battery.