MACS Monthly Newsletter - 2021 - DEC1

Service Reports
MOBILE AIR CLIMATE SYSTEMS ASSOCIATION ©
By Peter Orlando, Carquest Technical
Institute / Advance Auto Parts
Electric Cooling Fan Analytics
The modern internal combustion engine with all its advanced
technologies is still grossly inefficient. Even when
operating at peak efficiency, it's still only about 30-35 percent
efficient as machines go. This translates to approximately
65-70 percent of the heat of combustion lost to the
atmosphere. Much of this heat loss is released into the
exhaust and cooling systems.
The modern liquid cooled four stroke internal combustion
engine (ICE) must still be cooled by heat transfer
via the radiator via forced convection. It is considered
" forced " because the amount of heat transferred from the
coolant in the radiator to the atmosphere is highly dependent
on the air flow that is flowing across the radiator fins.
While the vehicle is in forward motion, a decent amount
of air is passed over the frontal area of the vehicle to provide
enough heat transfer to cool the coolant returning to
the engine. However, there would be insufficient air flow
across the radiator when the vehicle is moving slowly, say
in traffic, or while stopped. So, our cooling fan(s) provide
a way of supplementing the air flow during these conditions.
What
began decades ago as a mechanical fan attached
to the water pump with and without a fan clutch, has
evolved into a very efficient complex electrical motor control
of cooling the modern ICE as well as hybrid electronics.
I will spare the history lesson on coolant fan technologies
for the purpose of this article.
I would, however, like to spend some time exploring the
different ways manufacturers control their cooling fans
while explaining important electrical circuit characteristics.
Secondly, we will be demonstrating an analytical way
of looking at the cooling fan wiring schematics to determine
the diagnostic approach necessary to correcting
any cooling fan control or operating deficiencies.
Our approach to performing any electrical circuit testing
of the cooling fans should always begin with a thorough
inspection of the frontal area of the vehicle. Due to
the location of the heat exchangers, condenser, sub-condenser,
radiator and other fluid coolers, they are subjected
to all sorts of road debris encountered. This area creMACS
Service Reports is the official technical publication of the
Mobile Air Climate Systems Association, P.O. Box 88, Lansdale, PA
19446. The material published in MACS Service Reports expresses
the views of the contributors and not necessarily that of MACS. Every
attempt has been made to ensure
December 2021
1
ates a " catch all, " which results in conditions for air flow
restrictions. Air flow restriction diagnostics can be tricky if
the technician is not acute to its effects. Example: A 4WD
pickup truck may only be overheating while pulling a trailer.
The service writer and technician need to know this
critical information. It is not every day a condenser/radiator
restriction is found to be the cause of overheating,
and it may go uninspected. Additionally, if we are in A/C
season, these air flow restrictions can cause higher A/C
pressures, which will affect air conditioning performance
and create reduced passenger comfort. Cooling efficiency
in the radiator depends on sufficient air flow passing over
the radiator fins to absorb the heat from the hot coolant. A
coolant temperature drop between inlet and outlet of the
radiator can only be achieved if there is sufficient air flow
across the radiator. It is important to realize any obstructions
to air flow across these heat exchangers, regardless
of how small, can affect air volume and needs to be corrected.
Items
to Inspect:
Bugs, road dirt, oil, road construction materials,
animal remains, bent cooling fins, air dams,
gaskets and fan shrouds.
Any area(s) that are restricted can impede the
efficiency of the electric cooling fans, which can
result in cooling and air conditioning system performance
degradation. Obviously, this will all be
determined by the severity of the restriction.
A good visual inspection should include a
flashlight test across the entire section of the
radiator surface area. With the vehicle off, the
light is placed in the engine compartment facing
forward. This vehicle has 352,000 miles on it.
We can visually see there are minor condenser
fin restrictions and surface bugs that need to be
cleaned off. A garden hose or low-pressure power
washer may be all that is needed to clear any
surface debris (Figure 1).
the accuracy of the content of MACS Service Reports. MACS, however,
will not be responsible for the accuracy of the information published
nor will MACS be liable in any way for injury, labor, parts or
other expenses resulting from the use of information appearing in
MACS Service Reports.
MACS Service Reports
December 2021
MACS Monthly Newsletter - 2021

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