Have you had other service problems in the last few
(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.
Change 1 8-5