chap50 pps Automotive technology at University of Cambridge

start
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


OBJECTIVES:
After studying Chapter 50, the reader should
be able to:

•

Prepare for ASE Heating and Air Conditioning
(A7) certification test content areas:
—“A”(Air Conditioning System Diagnosis and
Repair), content area
—“B” (Refrigeration System Component

Diagnosis and Repair), content area
—“C” (Heating and Engine Cooling Systems
Diagnosis and Repair, content area
Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


OBJECTIVES:
After studying Chapter 50, the reader should
be able to:

•

•

Prepare for ASE Heating and Air Conditioning
(A7) certification test content areas:
—“D” (Operating Systems and Related
Controls Diagnosis and Repair), and
content area
—“E” (Refrigeration, Recovery, Recycling,
and Handling).
Diagnose lack of heat problems.
Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458

OBJECTIVES:
After studying Chapter 50, the reader should
be able to:

•
•
•
•

List the air-conditioning system performance
check procedures.
Discuss methods used to locate the source of
an air-conditioning system leak.
Describe how to recover, evacuate, and
recharge an air-conditioning system.
Discuss what is necessary to retrofit a CFC12 system to to use HFC-134a refrigerant.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper

UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


KEY TERMS:
bleeder valves
high-side pressure
low coolant level
low-side pressure

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458

HVAC DIAGNOSTIC PROCEDURE
When diagnosing a heating and air-conditioning system problem,
most vehicle manufacturers recommend the following steps:

Step #1 Verify the customer complaint (concern) Sometimes the
customer does not understand how the system is supposed to work
or does not explain the fault clearly. Verifying means that the tech
can verify that the problem has been corrected after service.
Step #2 Do a thorough visual inspection HVAC problems are
often found by looking carefully at all of the components, checking
for obvious faults or damage due to an accident or road debris.
Step #3 Check for diagnostic trouble codes Many systems use
sensors and actuators, which are computer controlled.
Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,

River,NJ
NJ07458
07458


Step #4 Check for related technical service bulletins (TSBs) If
there has been a bulletin released to solve a known problem, it saves
time knowing what to do rather than trying to find and correct.
Step #5 Determine the root cause Find and correct the root cause
of the problem. Low refrigerant level means there was a leak in the
system. Finding and correcting the leak correcting the root cause.
Step #6 Verify the repair Drive the vehicle under similar
conditions which caused the customer to complain and verify that
the concern has been corrected.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ

NJ07458
07458


HEATER DIAGNOSIS
Most heat absorbed from the engine
by the cooling system is wasted.

Some of this heat is recovered by
the vehicle heater.
Air is passed across the heater fins
and sent to the passenger compartment.
In some vehicles, the heater and air
conditioning work in series to maintain
vehicle compartment temperature.
Figure 50–1
The heater core is mounted inside a heater
plenum chamber where air passes over it to
absorb heat from the warmed engine coolant.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice

PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


HEATER PROBLEM DIAGNOSIS
When the vehicle’s heater does not produce the desired amount of
heat, many owners and technicians replace the thermostat before
doing any other troubleshooting. Many other causes besides a
defective thermostat can result in lack of heat from the heater. To
determine the exact cause, follow this procedure:

Step #1 If the engine is up to proper operating temperature, the
upper radiator hose should be too hot for you to keep your hand on
it. The hose should also be pressurized.
a. If the hose is not hot enough, replace thermostat.
b. If the hose is not pressurized, test it. Replace the
pressure cap if it will not hold specified pressure.
c. If okay, see step 2.
Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,

Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Step #2 With the engine running, feel both heater hoses. (Heater
should be set to the maximum heat position.) Both hoses should be
too hot to hold. If both hoses are warm (not hot) or cool, check the
heater control valve for proper operation. If one hose is hot and the
other (return) is just warm or cool, remove both hoses from the
heater core or engine and flush the heater core with a garden hose.
HINT: Heat from the heater that “comes and goes” is most likely the
result of low coolant level. Usually with the engine at idle, there is enough
coolant flow through the heater at higher engine speeds, however, the
circulation of coolant through the heads and block prevents sufficient flow
through the heater.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson

PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Water on the Carpet? Check the Evaporator
Water Drain.
If the evaporator water drip tube becomes clogged with mud, leaves, or
debris, water will build up inside the evaporator housing and spill out onto
the carpet on the passenger side. Customers often think the windshield or
door seals are leaking. Most evaporator water drains are not visible unless
the vehicle is hoisted.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.

Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


HEATER TROUBLE DIAGNOSIS
Lack of heat from the heater or heat coming out of the wrong
vents can be a dangerous and uncomfortable problem. The first
step in the diagnostic process is to perform a thorough visual
inspection and perform simple tests.
CAUTION: Do not remove the radiator cap when the engine is hot.
Allow the vehicle to sit several hours before removing the pressure cap tocheck the radiator coolant level.

Check the coolant level Low coolant level can cause a lack of
heat from the heater. It can also cause occasional loss of heat.

Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.

Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Carefully touch the upper radiator hose with the engine
running On most vehicles, the temperature of the hose should be
so hot that you cannot keep your hand on it (between 190° to
220°F [88° to 104°C]).

NOTE: An infrared pyrometer can be used to measure the temperature of
the upper radiator hose and the area around the thermostat housing.

Results: If the upper radiator hose is not too hot to hold, then the
engine thermostat is defective. If the radiator hose is too hot to
handle, then the lack of heat from the heater is not due to a lack of
hot water in the engine.

Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008

2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Carefully touch the heater hoses Both heater hoses should also
be too hot to keep your hands on the hoses. This test confirms
that engine coolant is able to flow from the engine to and through
the heater core and return to the engine. See Figure 50–2.
Results: (a) If neither heater hose is hot to the touch, it is likely
there is an air pocket in the heater that is preventing the flow of
coolant into the heater core. (b) If only one heater hose is hot to the
touch, then the heater core is likely to be clogged or partially
clogged. A clogged heater core would prevent enough hot coolant
from circulating through the heater core to provide adequate heat to
the passenger compartment.

Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Figure 50–2 A heater control valve. This valve is normally open, allowing engine coolant to flow
through the heater core. When the air conditioning is switched to maximum cooling, the valve
shuts off the flow of coolant to the heater.

Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.

Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Defrost All the Time? Check the Vacuum
A common problem involves airflow from the defroster ducts even though
the selector lever is in other positions. The defrost setting is the default
position in event of a failure with the vacuum supply. Defrost position is
used because it is the safest position. For safety, the windshield must
remain free from frost. Heat is also supplied to the passenger
compartments through defrost ducts and the heater vents at floor level.
If the airflow is mostly directed to the windshield, check under the hood
for a broken, disconnected, or missing vacuum hose. Check the vacuum
reserve container for cracks or rust (if metal) that could prevent it from
holding vacuum. Check all vacuum hose connections at the intake
manifold and trace each carefully, inspecting for cracks, splits, or softened
areas that may indicate a problem.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson

PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


HINT: This problem of incorrect airflow inside the vehicle often occurs
after another service procedure has been performed, such as spark plug
replacement. The movement of the technician’s body and arms can cause a
hose to be pulled loose or a vacuum fitting to break without the service
technician being aware that anything wrong has occurred.

The Hand Test
To check a radiator or condenser for possible clogged or restricted areas,
simply touch the outside of the unit with your hand. Any cool spots indicate
that the radiator or condenser is clogged in that cool area.

NOTE: An air bubble could be lodged in the heater core. This is a
common especially if coolant has been recently replaced. Failure to
properly “burp” the air from the cooling system can cause a pocket of air
to remain trapped in the heater core, preventing coolant from flowing.
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition

By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Part 1
How Can You Easily Burp Air From the Cooling System?
The first step in being certain there is no air in the cooling system is to try to avoid
getting air into the system in the first place during cooling system service. If the
engine is equipped with bleeder valves near the high spots of the cooling system,
these valves should be open when refilling the radiator. Any trapped air will always
travel to the highest portion of the cooling system and escape out of these bleeder
openings.

Close the valves as soon as coolant
is observed coming out of the valve
opening.

Figure 50–3
Many engines are equipped with a bleeder valve
to permit a technician to bleed any trapped air
from the cooling system. The valve is loosened
as coolant is poured into the system. Because
air is lighter than coolant, the air tends to float
toward the highest part of the cooling system.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Part 2
How Can You Easily Burp Air From the Cooling System?
If the cooling system is not equipped with bleeder valves, fill the cooling

system as full as possible and then start the engine. With the radiator cap
removed, the coolant level will often rise as trapped air expands, then
drop down as the air escapes out of the radiator neck opening. Air can
still remain trapped. To help speed the process, try installing the radiator
cap just to the first notch. (In this position the radiator cap is closed, but
will not seal enough to allow pressure to build in the cooling system.)
To help force any trapped air from the cooling system, simply drive the
vehicle normally for several miles. By driving the vehicle under load, the
engine will warm up faster and the thermostat will open allowing the
coolant to flow from the engine and through the radiator. Any trapped air
is then released into the radiator where it can easily escape through the
unsealed radiator cap. After filling the radiator, securely tighten the
radiator cap and test-drive the vehicle to verify proper operation.
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458

Hot/Cold/Hot/Cold Heater Diagnosis
A common customer complaint is a lack of heat from the heater but only
while driving, even through there seems to be plenty of heat when the
engine is at idle speed and the vehicle is stopped. This is a classic
symptom of low coolant level. The lower than normal coolant level in the
radiator prevents enough flow to supply the heater core. When the engine
speed is reduced, the water pump turns slower and coolant can more
easily flow through the heater core resulting in heat from the heater. As the
engine speed increases, the water pump speed also increases. Be-cause
there is less than the proper amount of coolant in the system, the water
pump will only be able to supply coolant through the engine (a path of
lower resistance).

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ

NJ07458
07458


CHECKING A/C SYSTEM PERFORMANCE
The first step in the diagnosis of any cooling system problem is to
verify the complaint (concern).
Step #1 Start the engine and turn the A/C
system to maximum with the engine operating
between 1500 and 2000 rpm with the doors
open. Operate the system for 5 to 10 minutes.
Figure 50–4 Many older CFC-12 systems are equipped with a
sight glass either on or near the receiver-drier. A fully-charged
(or completely empty) system is indicated by a clear sight glass.
Bubbles or foam indicate that the system is not fully charged.
An empty system may have oil streaks on the sight glass
being moved by the vapor remaining in the system.

Step #2 Verify by visual inspection that the
A/C compressor clutch is engaged. Check the
sight glass if the vehicle is so equipped
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

Continued

©©2008
2009Pearson
PearsonEducation,
Education,Inc.

Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


HINT: If the A/C compressor clutch cannot be observed, have an assistant
turn the air conditioning on and then off and listen for the “click” of the
A/C compressor clutch.

Step #3 Place an air-conditioning thermometer in the A/C vent
near the center of the vehicle. Wait several minutes to allow the
system to reach maximum output and observe the thermometer.
• If 35° to 45°F (2° to 7°C); system functioning OK. Continue a
thorough visual inspection looking for any faults that may cause
• If over 45°F (7°C), continue with pressure gauge testing (Step 4).
Step #4 Identify the refrigerant. Before connecting the pressure
gauges or performing any other service to an automotive airconditioning system, verify the refrigerant that is presently in the
system. Connect a refrigerant identification machine to the system.
See Figure 50-5.
Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Figure 50–5 A typical refrigerant identification machine. The readout indicates what kind of
refrigerant is in the system. If a blend or some other contaminated refrigerant is discovered, it
should be recovered and stored in a separate container to keep it from contaminating fresh
refrigerant.

Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.

Pearson
PearsonPrentice
PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Step #5 Connect both high-pressure and low-pressure gauges to
the service ports. The low-side pressure should be about 25 to 35
psi. The high-side pressure should be about 150 to 200 psi. Compare
your readings to the normal and abnormal readings in the following
chart. See Figures 50–6 and 50–7.

See the chart on Page 574 of your textbook.
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

Continued

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice

PrenticeHall
Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458


Figure 50–6 (a) Both high-pressure (red) and low-pressure (blue) hoses have been attached to
the vehicle. (b) High-side pressure can be compared to the temperature of the outlet from the
compressor. Here a service tech is using an infrared pyrometer to measure the temperature.

Figure 50–7 Hot refrigerant condenses in
the condenser when it loses its heat to the
outside air. Note how the level of the liquid
line changes when undercharged or
overcharged.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
PearsonEducation,
Education,Inc.
Inc.
Pearson
PearsonPrentice
PrenticeHall

Hall- -Upper
UpperSaddle
SaddleRiver,
River,NJ
NJ07458
07458