Plastic /Rubber smell from heater burner??

Hello, everybody I am new to this community and I am driving a freelandertd4 from 2004.The other morning I started the car and an awful plastic /rubber smell was inside the car,had a look on social media and apparently is the heater burner. Previous owner installed a swich in the cabin.When I chec8to see from where the smoke was coming lead me to the heater burner. Now while I was with the bonnet up a bubble sound came of the heater exhaust with some water and after some diesel fumes which forced me to take I immediately the fuse off and everything stopped. NOW...drove the car and the smell was still coming inside and not stopping as I was presuming taking the fuse off will do that.IWill like to ask if to put the fuse back.and take it off for few seconds to reset the ecu as I saw some advices??Please can someone help me as I dunno what to do with that smell ,car is running fine otherwise....thank you very much .

Is the Fuel Burning Heater (FBH) running?

Do you hear the inside blower running?

The FBH does make some smoke and smell, but it's definitely a burning diesel smell, not burning plastic.

I was thinking Positive Temperature Coefficient (PTC)? PTC being essentially an electric heater like the guts of a household fan heater tucked into the heater matrix box. With the FBH being under the inner wing, infront of the N/S wheel, behind the bumber, and the PTC being in the dashboard I'd say a PTC setup is more likely to be the culprit for plasticy smell inside the cabin. Especially given previous owner put it on a switch - eek!

Alex, if you have one of these auxiliarry fuseboxes inyour vehicle, with 3x30 amp fuses, its almost certain your car has PTC rather than FBH.