well basically my fan isnt cutting in. I've replaced the temperature sender unit, the thermostat and the sendsor that screws in to the radiator near the battery.

i know my fan works because i connected to the battery.

can anyone shed any light onto this please?

much appreciated :)

I presume you've checked the fuses and relays for the fans/cooling system? How have you checked the fan? Connected it directly to a 12v power source? And it spins I guess?

What makes you think that the fan isn't working - is the car overheating? What's the temperature gauge in the car reading?

Also check that the cooling system is working OK. Do both radiator hoses get hot? Could there be air in the system?

fuses and relays are getting checked today

and yeah i connected it to a 12v battery and it spun :)

and 'missinglincs' i could be driving along and the car heats up as you would expect, gauge is at the middle.

then if I'm sitting in traffic for about 5mins the gauge starts to increase. both hoses to get hot yes.

do you think i should flush the system?

and could it be the radiator?

thanks guys

It does sound as if its electrical problem then.

You could see if the circuit is OK by bridging the temp switch on the radiator. Connect the terminals together and see if the fan comes on?

If that works, the switch is faulty.

Otherwise its a case of working through the circuit looking for breaks, loose terminals, broken wires or bad earth.

No relay for the fan on these, there's a power feed off the battery through a fuse on top/side of the battery, goes to a thermostatic switch (screws in the side of the radiator) and finally to the fan.

Had taken mine out for a job and forgotten to put it back in, was fine until the car was stationary for about 5 minutes then the temp gauge started to creep up - I'll bet yours is blown or not present, or an earth fault. Get a multimeter out, check for 12V at the fuse and at the thermostatic switch (pull the plug off the back, check the wire that comes from the battery - red probe on the terminal, black probe on the battery negative)

If you've got 12V there, check for continuity between the terminals from the back of the fan and the battery negative post (switch to Ohms mode or beeping continuity tester if you've got that function on your multimeter)

http://www.maplin.co.uk/tools/test-equipment/multimeters - second one down is one that I've got for in the car, better than the yellow "domestic multimeter" that really is a pile of cack

Edited 27 January, 201115 yr by majic79

are you talking about the little junction box/fuse holder thing on the possitve side of the battery?

and il try the mutlimeter thing tomorrow mate.

also the 2 sensors at the front of the thermo housing.....I've changed the one on the right (temperature sender unit) but whats the left 1 for? i aint changed that 1

i checked all my fuses and there all fine

The other sensor is what's most likely the problem, the fan control switch. Try bridging it and see if the fan starts.

which 1 is the fan control switch?

and i bridge them all 1 by 1...then il knw lol

two senders on the thermostat housing are 1) Dash Temp Gauge Sender and 2) ECU Temp Sender - this is used to see cold the engine is and enrich fuel supply. Fan control is by a thermostatic switch in the side of the radiator.

If you want to test it, boil the kettle, put the switch in the boiling hot water and stick probes across the two terminals. You should have no continuity across it below 80c (or thereabouts) and then it will suddenly start to conduct (allowing electric to flow and switch the fan on)

Simplest circuit on the car, check the little junctionbox/fuse holder on the side of the battery - if you've got a manual car with no ABS, there should be just one fuse there. Also worth swapping your thermostat - might be blocked and the radiator never sees full temperature of the coolant so never sees a need to switch on

right... i brigded all the sensor today but it was with a bent split pin.. all the sensors r new other then the ECU one (green i believe)

I've checked all fuses and they all ok. (the box on the battery and the fuse box)

I'm guna get a new thermostat and flush the system out. il try the bridging the fan control terminals into boiling water...

what about if i used VAGCOM? could that tell me?

thanks to all you guys...greatt help

I'm guna get a new thermostat and flush the system out. il try the bridging the fan control terminals into boiling water...

what about if i used VAGCOM? could that tell me?

thanks to all you guys...greatt help

Probably a good idea - if it's full of muck it'll cause problems

VAGCOM will probably only tell you that the engine's got hot - not much else you didn't already know

I'm guna purchase a new ecu temp sender and flush out system, and vagcom it (other faults need to be delt with)

see what happens then

:) :)

Not sure whether this is right or not but thought it'd be worth chucking out, perhaps it's the water pump? If everything else (fuses/switches/fans) are working correctly then that's pretty much the only thing left? If the pump isn't circulating the water then the engine will get hot but the thermostat won't be receiving any hot water, meaning that it won't open and set off the fans?

As I say, I might be talking rubbish and if I am feel free to tell me/put me straight!

Could be the fan control unit, mounted by the battery?

can u put a photo of the fan control unit up please mate? dnt knw where it is?

and I'm not sure it it could be the water pump? I'm guna change that aswell

the ecu temp sender was ordered today £12 quid +10% off for being a VR6OC member ftw

I'm guna price a water pump up aswell, tbf it might aswell get done as its due a service

I have'nt got a picture but this from Vagcat item #1 I think it's mounted near the battery

3A0919506 electric fan control unit / to be used for: / use if required: 357 919 506/A N 017 125 2 /

Edited 2 February, 201115 yr by nige8021

haven't got a clue where that is, I've had a look and cant seem to find it

i installed the ecu sender unit today......car heats up as normal....but fan still dosent kick in, but it didnt go over tempurature either. so it good be good and a bad thing lol

according to that picture there is a fuse in the unit. if i find it I'm check that.

Found this #13 is the fan control unit

il have another look but I'm 90% sure there is nothing that looks like that on my polo....theres a one on my vr6, so i sorta knw what it looks like.

but defo not 1 on my polo :( arrgghhh!!! lmao

great help tho matey (y)

just been out to have a look, and i think I've found it... is it under the chasis leg? next to the horn?