Is there a U Pull It or Pick a Part wrecker in your area? I have read that the Polo & mk3 Golf have the same controls. I don't know what years though so you will need to take a look. The actual facia will be T4 only.
As Sunny has said, lube the cable. You may need to replace if it's rusty. It seems to be fairly normal for some owners if something is stiff, just use more force until something breaks. On my van the valve was installed at the wrong angle in the hoses so that the cable dragged on the rubber hose. It was obviously like that for a long time[maybe from new] because it was cutting through the hose. I was looking under the bonnet, soon after buying the van & spotted it. It may have lasted but for piece of mind I replaced the hose. I am into reliability.
Understand how it works, troubleshoot logically BEFORE replacing parts.
2001 T4 TRAKKA Syncro 2.5TDI,2006 Mk5 2.0TDI Golf manual,2001 Polo 1.4 16V manual [now sold], '09 2.0CR TDI Tiguan manual,
Numerous Mk1 Golf diesels
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