More MFTS problems!!

[NickGrasse]

So I changed my MFTS (ABY engine) after getting the overheat signal, problem sorted, but now the fan won't cut in at 95degrees and the temp gauge is reading higher than it used to, about 2 lines above the 90 mark.
Two questions;
1/ as I also renewed the plug which fell to bits, has anyone got a wiring diagram as the colours on my wires are different to those on the autotechnik info; i have Black/Blue (redundant for 3 connector switch) Brown/Blue, Blue/White &Blue/Yellow- perhaps I have wired it in wrongly so I want to check the functions
Secondly, is there a link between the MFTS and the fan circuit? I have checked the rad sensor and the fan works when I jump wire the plug which plugs into it. The fan only cuts in at about 110 degrees.
Any input would be helpful, at 220k miles my motor has never been apart and I don't want to blow the head gasket now!

[rs200]

i have a same problem on my 3b.
the water starts to cooking and the fan is still off.
I went to audi service to buy a new one fan tem. sensor, and the problem was same.

than one somebody tell me that the audi have big problem with this 3 pin tem. switch. i go to next door auto parts store and buy a tem. switch from citroen BX ( 2 pin- 95 degrees) , take out 1. and 3. pin from my connector switch , put it on 2 pin switch and it works perfect today , just like before 3 years, when I done this.

[AUDIS2avant]

Normally you have to buy an original MFTS sensor, to get the correct readings from the gauge, it has to read 90 - 1 / 90` @ normal and fan start just after 90 + 2 but if you have an unoriginal mfts sensor then it reads 90 + 2 @ normal and fan starts just after 90 + 4.

[bigdan]

Normally you have to buy an original MFTS sensor, to get the correct readings from the gauge, it has to read 90 - 1 / 90` @ normal and fan start just after 90 + 2 but if you have an unoriginal mfts sensor then it reads 90 + 2 @ normal and fan starts just after 90 + 4.

I have an 'unoriginal' one fitted, and it reacts in the same way i.e normal temp = 90 + 2 and fan cuts in at 90 + 4.

I have checked the cooling system with a pyrometer, and didn't get a reading above 90degC, so i'll assume the engine is cooling ok and that the new 'unoriginal' MFTS is at fault. HTH

[NickGrasse]

Well thankyou guys, this is reassuring. FYO this sensor was from Eurocarparts, £54.00, Audi's quoted me £108.00!!
I'll see if I can borrow a pyrometer to check this.

[archiboy24]

Make sure you've really bled the cooling system thoroughly. The fan not coming on can often be caused by an air pocket.

[johne]

Two questions;
1/ as I also renewed the plug which fell to bits, has anyone got a wiring diagram as the colours on my wires are different to those on the autotechnik info; i have Black/Blue (redundant for 3 connector switch) Brown/Blue, Blue/White &Blue/Yellow- perhaps I have wired it in wrongly so I want to check the functions
Secondly, is there a link between the MFTS and the fan circuit? I have checked the rad sensor and the fan works when I jump wire the plug which plugs into it. The fan only cuts in at about 110 degrees.

Wiring details are available on S2Central.net

There is no link between the radiator fan and the MFTS. As others have suggested, your new MFTS is causing your temperatue gauge to read high and your fan is working as it did and as it should.

John