The rear heater is really easy to work on. Mine had a fine core but the
plastic lining of the wood enclosure had come off and apparently shorted
out the fan motor and melted the housing. This explained the hot smell
without heat. I found an entire core/fan at a junkyard and replaced the
whole unit, only to find out my "new" one leaked, so switched back to my
old core with "new" fan. Easy. But very messy; get lots of towels ahead
of time.

Scott
'74 unnamed Thing
'83.5 Westy "Moovan"
'99 Millinium Bug