UK-POLOS.NET - THE VW Polo Forum

Hi All,

Got an overheating problem with my 9N3 1.2 petrol.
Driving around day to day, its all good, temperature gauge sitting at 90. Sit in traffic for 10 - 15 minutes and its alright. However sit in stationary/stop start traffic in hot weather and the temperature creeps up before eventually giving the overheat warning at 130. Get back to a more steady driving speed and the temperature goes back down and sits at 90 as if nothing happened.
If I switch the AC on, fan kicks in and holds the temperature down a bit longer. But on hotter days it only holds it below 110 and at 90 with the help of the heating on full blast.
Suspecting a dud fan switch, I had it replaced, but nope, still overheats.
Also checked all the fuses. Doubting the thermostat as it gets to running temperature and holds fine as long as moving.
Now I am fresh out of ideas.

Any help would be greatly appreciated.
Iain

Hi Iain - does the cooling fan cut in automatically at all ?
Does the cooling fan work ?

I think that you will find, if your car is fitted with a single electric cooling fan, that it has a slow speed and a high speed mode of operation. The slow speed is achieved by using a series dropper resistor and it is this resistor that fails normally. I'm sure that you have never checked this as you will always be in heavy traffic when over temp warning comes on, but, does the fan eventually switch on at the higher speed, maybe you can hear that though if you have wisely used the AC to switch that fan on or used the cabin heater fan to cool things down you will not be able to comment on that.

There is a fan control unit fitted to these cars so maybe it or its wiring is faulty if the fan slow speed wiring is okay.

Things to check, if you are able to do this, unplug the thermal switch and link two of the pins see if each fan speed can be commanded by doing that. To find out what or how to do that, maybe Google "VW Golf fan not working" - as all these cars use roughly the same components etc.

Thanks for the replies.
So, some other recent diagnostics.
Using an illuminating tested to test there is power going to the fan switch; there is power and the fan switches on.
Bridging the connection between the power pin and pin no. 2, fan comes on at low speed. Bridge it to the other terminal, fan does not come on at high speed (even with the ignition on, which was suggested on another thread).
Now the fan has stopped coming on when the AC is switched on.

Iain