I know this subject has had a lot of information posted but can't find an answer to this. My heater fan works fine on settings 1-3 but I get nothing on 4. I know if the resistor is faulty then it should only work on 4 but not seen this issue before. If anybody could help me out here it would be much appreciated.

Have you checked to see if the connectors are ok & not overheated, requiring a new connector block.
I believe this is all covered by the common faults sticky though.

See FAQ section

Oh sorry didn't see that. Thanks for your help.