WD Catalog 2018

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Troubleshooting
& Service Procedures
• Troubleshooting Overview
• Understanding System Function
• A Troubleshooting Example
• Manifold Gauge Set Installation
• Troubleshooting by Manifold Gauge Set Readings
• Review of Frequent Problem Areas
• Conclusion
Can you fix an air conditioner or heater system without finding and
correcting the cause of the problem? You bet you can! It happens every
day and it’s not good for business. Here is an example. A truck pulls in off the
road and the operator asks to have his rig serviced in a hurry. He tells you the
air conditioner isn’t cooling like it should and dashes into the restaurant for
lunch.
You tip the hood, and check the sight glass on top of the receiver-drier. You
see bubbles, not a lot but a fairly constant stream of them. It is obvious the
system is low on refrigerant so you hook up the manifold gauge set, purge the
gauge set hoses of air, and add refrigerant until the sight glass clears. Then you
check evaporator temperature and it’s OK. The air conditioner is repaired
right? Wrong! What you did is add refrigerant and the problem went away. You
did not find and fix the cause of the problem.
Component failure in an air conditioning system may be the result of a
problem elsewhere in the system. For example, a belt or clutch failure might be
caused by a dirty condenser restricting air flow and increasing head pressures.
High head pressures commonly create problems with other system compo-
nents. Take time to look beyond the obvious for a potential hidden
problem.
Troubleshooting Overview
Troubleshooting includes collecting enough information to locate the cause of
the problem, then correcting the problem and its cause by replacement, adjust-
ment, and/or repairing. You begin by gathering information from the most to
the least important sources.
Starting with the most important:
1. Your personal knowledge and experience with AC systems.
2. The vehicle operator's knowledge and experience—question him or her.
3. The work order.
4. Good test equipment and the HVAC system
The routine you follow when troubleshooting should proceed from the most to
least productive way of locating the problem and fixing the cause.
8
Chapter
8-1
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