Hot air... whiff?

Sorry guys, this is a bit of a pathetic question, but my other half thinks my Amazon has mice, because when the hot blower is on there is a definite 'mousy' smell. It isn't there when the lever shuts the hot air off. Is there anything that I can put in the airflow system to sweeten up what comes through? I suppose I should get the heater core thoroughly cleaned out, but want to avoid this extra expense if possible? Thanks Tom

You might have a small leak in the heater matrix. Hot anti freeze can have a bit of a pong.

Interesting, Derek, thanks for that; I wouldn't have thought of it, but will now get it checked. Tom