ACtion Magazine - June 2016 - (Page 14)
Interior heat shields
By Steve Schaeber
nterior heat shields are not used on every single car or truck, but we find
them often enough that most technicians can remember seeing them
here and there. Installed for a variety of reasons which may not be immediately apparent, they're an important part of the overall engine cooling
system that must be replaced following service, and not left off or forgotten
about after being removed.
Interior heat shields serve a variety of functions, with perhaps the
most important being to control the unwanted transfer of heat inside the
cabin area. They're usually installed above the passenger footwell directly
below the HVAC housing, but can also be found above the driver's area or
in other places near the console or dashboard.
Often it is necessary to remove these shields to gain access to various HVAC components, such as blower motors, resistors, heater cores,
evaporators, actuators, linkages, vacuum lines, etc. Unfortunately these
shields are sometimes thought to be unnecessary or too time-consuming
and difficult to reinstall so they are not and in some cases are even discarded.
But they play an important role, not only in maintaining interior temperature, but also in controlling noise levels. Insulation is often attached
to one side of the shield, which functions to control temperature as well as
sound. Some blower motors are quite noisy, and these shields can be an
effective means of keeping that noise to a minimum level.
They can also serve to guard HVAC components against damage
ACTION * June 2016
from below. Many technicians have seen vehicles with broken vacuum
lines, disconnected cables or damaged wiring likely caused by someone's
foot, bag or package getting caught, or maybe a toy that became tangled
up in the works.
Mazda has identified an instance where some MX-5 customers may
complain that the temperature is too hot around the passenger footwell
area. This is caused by heat radiating from the heater core (which is positioned at the bottom of the HVAC case), but it's not due to any component
defect or failure. With normal engine coolant temperatures in the range of
177 to 193°F, it's simply due to the proximity of the heater core in relation
to where a passenger may rest their feet. If their legs are stretched out so
far as to place their feet close enough to the HVAC case, they may notice
and complain of the increased temperature in that area. However, if they
sit in such a position that places their feet closer to the seat bottom (and not
so near the HVAC case), they might not notice the difference.
To address the situation, Mazda has issued Service Bulletin number
07-001/16, Passenger Side Footwell Area Too Hot From Heat Radiated
by Heater Core. In it they describe correcting the problem through the
use of an insulator constructed from a urethane sheet (P/N NA1P-61-J13),
which attaches to the underside of the HVAC case to decrease the surface
temperature. In effect this sheet acts to block the transfer of heat, thereby
reducing the temperatures felt by occupants. ❆
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