taminants in the environment can plug the cabin filter
quickly, restricting airflow and putting more load on the
blower motor. Particles that get past the filter can glom
on to the evaporator core, impeding air flow and maybe
causing a musty smell. Inspect the fresh-air intake and
recirc filters at least once a month and change them out
as needed.
photo: MACS staff
Evacuation and charging: Big, heavy-duty A/C systems like the ones in a fire truck have long hose runs,
large coils, and tube-and-fin condenser assemblies with
multiple passes. There are plenty of tight spots and low
points where oil can hide. When servicing the refrigerant system, flushing is the best way to make sure you've
removed all the oil before recharging the system.
With two evaporators, it's a big system.
When you evacuate the system, be sure to pull and
sustain a deep vacuum to micron-level accuracy. A good
vacuum pump and a thermister-based digital gauge will
help you do a precise and thorough job.
One reason A/C repairs tend to be costly is because
there's less emphasis on preventive maintenance than
there is with other systems on the vehicle. Too often, the
A/C gets attention only after it fails. No community can
afford to park an emergency-response vehicle because
the air conditioner didn't get the attention it needed. A
quick check during an oil change or any scheduled maintenance procedure means the A/C system will receive
service while it's there in the shop and be ready to keep
the windshield clear and the crew able to perform during
an emergency. ❆
Thanks to RED DOT for their help in completing this
article.
20
ACTION * July/August 2014
infographic: MACS staff
Fire truck air conditioning
Table of Contents for the Digital Edition of ACtion Magazine - July/August 2014