Volvo: bad odor from heater after replacing heater core, gasket material, heater core

Question
QUESTION: Greetings,
My '94 940's heater core was replaced several weeks ago by my mechanic.  
Upon
getting my car back, when I turned on the heat, with or without the fan, an
very
sharp burning odor occurred.  I ran the heat w/ the fan on at full blast for
extended periods to try to eliminate the smell, but it persisted.  I asked
around,
and one mechanic suggested that the insulation around the heater core was
faulty and burning.  My mechanic re-opened the car, removed the insulation
that
came with it and closed it.  Unfortunately, while weaker, the smell persists.  I
saw
the car when it was re-opened and noticed that what appeared to be small
particles of disintegrated gasket material was in the bottom of the heater
box.  
I've also noticed that when I turn the heater onto high with the fan on full
that
little black rubbery particles come out of the ducts (I put cheesecloth over the
ducts to see what was coming out).  Is it possible that the smell is the result
of
the gasket material blowing onto the heater core and burning there?  I
imagine
that my mechanic did not clean up the disintegrated gasket material in the
heater box...only removed the new insulation around the core.  Have you
heard of
this issue before?
Thanks!

ANSWER: Peter,
You might try to ask the shop you deal with to use something that is made to kill the mold in/on the heater case. To see if that clears it up..

---------- FOLLOW-UP ----------

QUESTION: Dear Ray,
Thanks for replying to my question.  The smell emanating from the heater
does not smell like mold but like something that is being heated up. When the
heater box was exposed at the mechanic's we removed a small piece of the
insulation that came with the new heater core and heated it up with a heat
gun.....the smell was the same acrid smell coming out of the heater.  I'm fairly
certain that the old gasket material or some insulation being heated might be
the cause of this very pungent smell as little bits of rubber/gasket seem to be
blowing out of the heating ducts when the fan is on high.  Have you heard of
this material settling onto the heater core and melting there, causing a sharp,
somewhat acrid, unpleasant burning smell?  Is it necessary to completely clean
out the heater box before re-assembling?
My mechanic is stumped...I'm stumped...he has taken the thing apart twice
now (once to install the new heater core, once to remove the new insulation).  
He's resistant to doing anything else, unless I can provide an explanation of
the cause.  I'm hoping to regain a functional heater (it's too smelly to use now).
I'm hoping that perhaps you might have heard of such an issue and have a
possible explanation.
Best,
Peter

Answer
Peter,
I have not heard of any insulation problem or burning of insulation. Most times I use a factory heater core to insure fit and quality. Maybe the core you have is an aftermarket that is having a problem with insulation. At the point you are at now, your only choice is another replacement. As you have shown that the smell is from the heater core and or the insulation.
I wipe out the heater case to get out any left over anti freeze, but that is about it.