I agree with the window..
Question: IS there an "Armoa"
Water has no smell, A/C condensate may tend to have a "moldy" or "Earthy" smell
Coolant (Heater core) has a sickly sweet smell.
No need to answer since I gave you the next level alrady. As far as I can go save for this
1970's both GM and Ford, changing heater core (Cars)
Book says drain cooling system, Nobody does that (Then or now) Clamp hoses (Hemostat style)
Remove hoses from heater core
Remove about a dozen screws from heater core cover
Lift off cover, insulation pad and lift out core
Drop in new one (or rebuilt) replace pad, cover, screws, pre-fill with antifreeze, re-attach hoses, Run engine till warm, Top off radiator
Today
Clamp hoses and remove (Book still says drain)
Evacuate A/C disconnect lines at firewall cap and seal.
Dissassemble dash (passanger side on most cars)
On Renault remove steering column (I kid you not)
Slide A/C evaporator out on it's rails (most cars) and remove heater core
Renault you open heater core compartment and remove
Re-assembly is reverse (Same as before)
I mean why do a 10 minute job when you can take hours?
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times