Cold draught coming through kitchen plinth fan heater

[ACJane]

We have a fitted plinth fan heater (Dimplex brand) and there's a terrible draught that comes through it. We don't really use it but equally I figure it's good back up when if the heating broke.

What could I do about the draught? At the moment I'm covering it with a towel (obviously it's off otherwise this would be unsafe).

I've looked to see if Dimplex do some sort of cover but they don't.
Any clever solutions? I wonder if it wasn't fitted properly given the gale coming through it?

I don't think this type of heater is vented to outside so there must be a hole somewhere behind the cabinets where the draught is coming in. You might need to remove the plinth and investigate.

That's so useful, thank you.
It's very feasible that this is the case as the back of the cabinets is always freezing.
Perhaps the air bricks are causing it?