If the heater fan only blows on the highest number is it the switch or the motor that's knackered?

 

reostat (and that has to be spelt wrong) in most cases. It's close to the blower fan/motor

 

if it's that can it be bought separately?

 

what is it on ??

its normally the resistor pack burning out and can be bought separately , although chances are the plug for it has melted too , on my mondy its fixed by one screw next to the heater box under the dash on the passenger side , as far i know most fords are a similar setup

 

what car is it? that would help

if it's a sierra one then it's the resistor thing on the actual blower motor thats packed up
a few screws and swap it over and job done

on some mondeo's it's been known that you need a lot of wiring to be sorted to get it working again as it burns out

 

forgot to say it's on 97 Vw Polo!

 

cant say i have ever worked on a polo !!!

i would guess it is similar setup anyway

 

Same thing happened on my mondeo cost no more than 10 quid for the part and 3 minutes to replace it, then again not sure on a polo but should be similar