I was wondering if any one had encountered a problem with there heaters, when the cars at temperature on a long run the heaters are hot but if I stop at traffic lights it goes cold, had the thermostat changed last month, some one said it could be the water pump, any ideas?.

Edited 24 November, 201312 yr by pants vrs

Try blowing the dust out of the sensor holes. You may have to replace the sensor. The climatic system is pretty simple for an automatic system, but everything has to work properly for it to work consistently.

Which sensor? Temp sensor?

I used to be able to watch temp guage fall when in traffic, I replaced belly tray and put a piece of perspex infront of rad / behind grill and removed if going on long journey or was warmer that day 

Which sensor? Temp sensor?

Yes, there is an air temperature sensor in the dash. It looks like 3 x 1cm long slits. It's not widely known that the Fabia features a very basic form of climate control and the heater decides what temperature to put out based on the cabin and outside air temperatures. If the sensor isn't working or is blocked (or you put a hot cup of coffee in the cup holder under the stereo) it can get a bit confused and blow odd temperatures out of the vents.

I used to be able to watch temp guage fall when in traffic, I replaced belly tray and put a piece of perspex infront of rad / behind grill and removed if going on long journey or was warmer that day

Sounds like a duff thermostat?

I replaced it