Radiator fan runs all the time, what should check?

[Jonas_R]

Well,

My main radiator fan has just started to run all the time on very high speed.

Have tried this so far:

Checked all fuses listed on s2central and they are oki.

Tried to switch around the relays in box under the hood, made no different.

So what else could cause this? Could it be the radiator fan switch and is it the same switch thats is mentioned in this thread:

http://www.s2forum.com/forum/showthread.php?t=4070

/Jonas R.

[Greg_S]

check the MFTS which is on the side of the block on the water manifold. it will be either 3 or 4 wire.

By having a short on that the rad fan will run all of the time i believe.

[Floppy]

What's the temperature? Above 90 it''s going to rotate at full speed. Correct me if i'm wrong

[Jonas_R]

Floppy:
Well this happens all the time also when the engine is cold, so has nothing to do with temperature i guess. This of course depends on how the radiator reads out the temperature?

Greg_S:
The MFTS is pretty new, but will check if there is any shorts.

/jonas R.

[Floppy]

http://www.s2forum.com/forum/showthread.php?t=7881&highlight=radiator+fan

here you should find some answers

Good luck!

[porkkis]

MFTS has nothing to do with rad fan. Try to unplug the rad temp switch at the bottom of the rad. That's probably faulty.

[Jonas_R]

Thx porkkis will give that a go.
Can you explain what the speed signal is? that is mentioned in the thread that floppy links to.

/Jonas R.

[porkkis]

Errm no it isn't or then I'm bloody blind.

[Mikes2]

Check also the resistor pack. Blue L shaped item under the washer bottle.

[Jonas_R]

Mikes2: will check that resistor pack

Porkkis:
Sorry was this thread i was talking about, in the end:

http://www.s2forum.com/forum/showthread.php?t=1043&highlight=radiator+fan

/Jonas R.

[porkkis]

I still don't know what you're talking about. Please quote the text you want me to comment.

[S4-rider]

The temp switch in the front radiator triggers the relay.
The relay triggers the fan via the resistorpack.
So both circuits are seperate (a signal circuit and one power circuit)

The temp switch on my S4 has 2 switches inside .
One is ON if 92 degrees is reached.
And the other comes in at 102 degrees.
Each switch has its own relay.

[Greg_S]

I always wondered what that blue bit of metal was

[Jonas_R]

Porkkis:
I dont know where i read that stuff with speed signal, think i must have been sleeping or something. Sorry for the trouble.

/Jonas R.

[porkkis]

Only thing I can think of is that you mean why the A/C unit uses the signal?

Older style A/C reduces the blower speed when vehicle speed increases as the air flow outside the car pushes air in.
Newer style probably does the same but it additionally has a air flow flap run by a servo motor in the intake shaft.

HTH