WD Catalog 2018

905 / 1003

8-5 - -
A Troubleshooting Example
• Have you had other service problems in the last few
months?
Answer: No.
• (If the answer was yes, you should ask—When? Where?
What was fixed or replaced?).
• Finally, ask the operator if he or she has a wiring diagram
for the system.
Now let’s look at the information you have gathered from the operator and
what you know from experience. He believes the problem is that the AC system
quits cooling after it has been on for a while! You know that the AC system has
not been maintained since the rig was purchased a year ago. Because of that,
there could be several causes for the problem (lack of cooling) and there may be
other potential problems about to develop.
It is possible that some refrigerant has leaked. Moisture and other contami-
nation may be inside the system. You have been told there are no heater
problems, but that doesn’t mean there are none that might affect AC system
operation. The AC system has quit cooling several times in the last few days.
The problem may have become more severe than when it quit cooling the first
time.
If enough refrigerant or oil has leaked out, a low pressure cutout switch may
have cut the circuit to the clutch, protecting the compressor. Because the
system has not been maintained in a year, there may be other components that
should be serviced. You could fix the probable causes, and the system might
work and then break down again as the rig drives out of your place. From your
knowledge and what the operator has just told you, you know this may not be a
quick fix problem.
It’s up to you to describe the service situation to the operator. Tell him you
need to do a complete system maintenance inspection to find and correct the
problem or other potential problems. He can give you the go ahead for full
service and repair now, wait till you have inspected the system to determine
cause and cost, or delay repair until he has some down time available.
Normally when the operator can tell you what the problem is, you would first
operate the system to verify the problem. In this situation your troubleshooting
(your own knowledge added to what the operator told you), indicates the next
step. You need to do a complete maintenance inspection instead! Proceed as
described in Chapter 7. Correct any obvious problems and check carefully for
leaks. Leak testing should be visual, by feel and with a leak detector. Next, do
your performance test with the engine running and the AC system on.
Note: Don’t forget to check the heater system too! If the
water valve is not closed, then hot engine coolant
flowing through the heater core would warm the air
at the same time the evaporator was trying to cool it.
The result would be the appearance of an AC problem.