MACS Monthly Newsletter - 2021 - JUN2

FCA

nections to inspect. The LTR runs at low pressure, typically
5 psi (or even atmospheric pressure), but using the same
anti-freeze water solution. So, although a low pressure
circuit would appear to be a lower leakage threat, all the
additional hoses and connections filling the powertrain

Figure 3: Wheelhouse view of the condenser, labeled (1).

techauthority.com

with a 1.3-liter turbocharged four-cylinder engine. This
model actually is made in Italy, on the same platform as
the Fiat 500x (Figures 2,3).
Water-cooling the condenser has obvious advantages,
primarily greater thermal efficiency in very hot weather
and the opportunity for improved packaging. Both the
condenser and charge air cooler, instead of taking up a lot
of the limited space as individual heat exchangers at the
front end, are remotely located in the engine compartment
as part of a water cooling loop to a single low-temperature radiator, which is mounted just behind the automatic
transmission oil cooler, but in front of the high-temperature radiator for the engine (Figure 4). The Renegade
condenser is located at the right front side of the powertrain compartment. This illustrates a basic packaging
advantage for a Low Temperature Radiator (LTR) system:
the liquid-cooling heat exchanger (i.e. condenser) can be
mounted very close to the compressor, the primary component of the circuit that it's cooling. Engineering studies
at Fiat (today they're called Stellantis) research showed a
5% improvement in fuel economy during A/C operation.
The LTR system can cover more than the A/C system. It
also could include a " water " circulating circuit for the turbo charge air cooler, cooling for the motor electronics of
a hybrid, perhaps even cooling for a smaller battery pack,
such as for a plug-in hybrid. So, you're likely to see a number of applications such as these on other cars. Although
there's a plug-in hybrid for this Fiat platform in Europe, it
isn't sold here yet.
The low-temperature cooling circuits raise a number of
service issues. First, there's the additional heat exchangers (at least two), and additional coolant hoses and con-

Figure 4: Renegade cooling system layout. Parts are (11)
automatic transmission oil cooler, (12) low-temperature
radiator, (13) high-temperature radiator, (14) auxiliary coolant pump, (15) turbocharger (16) 2 mm orifice restrictor,
(17) water-cooled condenser, (18) water-cooled charge air
cooler for turbocharger.
compartment are not immune to leakage. And if one of
them, or one of the additional heat exchangers leaks,
you've got to find the leak and hopefully source replacement parts, without a significant delay. And even though
there's an efficiency advantage of putting the condenser
close to the compressor, additional heat exchangers do
take up space and can make underhood service more
time-consuming. v

Humidity Sensors for A/C, Defrost Control
Relative humidity (the amount of moisture that air can
hold, which varies according to ambient temperature, divided by actual moisture in the air) is a primary factor in
passenger car cabin comfort in warm weather. The higher the temperature, the more moisture that air can hold.
Reducing that humidity is actually a primary function of

June 2021

automotive air conditioning in most geographic areas.
Just take note of all the condensate that drains from the
evaporator case if you didn't realize this-that's the auto
A/C pulling moisture out of the air that's going into the
passenger compartment. The higher the relative humidity, the less additional moisture the ambient air can hold.

MACS Service Reports

http://www.techauthority.com

MACS Monthly Newsletter - 2021

Table of Contents for the Digital Edition of MACS Monthly Newsletter - 2021