Taking Charge of Alternator Problems
Single Engine Alternator Charging System Troubleshooting
By Winston Greer and Mike McCluskey
If you've ever had an "out-of-box failure" of a replacement alternator then you need no description of the frustration you felt when that happened. If you haven’t had that experience then no description will do it justice. Technical Reps and Warranty Administrators develop this same sense of frustration when a returned "out-of-box failure" unit tests to specifications.
Aircraft charging systems occasionally present a real troubleshooting challenge. As Tech Service Reps, we would like to minimize your frustration and ours by offering the following insights for solving commonly encountered problems. Given the complexity of the charging system, the information presented in this article will be necessarily brief. We will focus on the "high spots" of alternator troubleshooting. Other related components and some of their effects will also be addressed.
Throughout the years, we’ve received numerous calls requesting technical assistance with charging system problems. About the time we think we have heard it all something new comes along. The old adage that "You can never know it all" certainly applies to alternators! The only consistent factor is that two basic scenarios exist. The first scenario is "It was working OK and now it isn’t," and the second scenario is "I just installed it and it doesn’t work." This second scenario can be much more insidious and difficult to troubleshoot, especially if you are uncertain as to the failure mode that caused you to change the component in the first place.
At a risk of pointing out the obvious, your first step should always be to verify that the alternator was correctly installed. Is everything properly routed and secure? With belt-driven units, is the belt tension proper? These questions and others equally apply to units that "fail" soon after installation.
"If all else fails, read the directions"
Manufacturers frequently include installation instructions and some even include a test report packaged with the unit. Occasionally, parts dispatchers remove this information so as to include them in the customer’s file. Sometimes these papers actually end up being discarded with the thought of "helping" the mechanic by removing extraneous tags, etc. If you deal with a dispatcher in your organization, ask if you can look over any information that came with the unit. If a manufacturer’s bench test report shows that the unit came off their production line operating properly, then it’s not likely any fault lies with the replacement unit. If you are the one who actually opened the box and you are sure there are no directions or test reports included, look for other contact information such as the manufacturer’s telephone or fax number on the box or data plate, even a web site or email address. In many cases, the manufacturer has a toll-free number to call for technical assistance.
Spend a few moments reviewing installation instructions and performance criteria (see Figure 1). This exercise may prevent you from removing a good replacement unit and installing yet another potentially misdiagnosed "out-of-box failure." Confirming how the installation is to be performed correctly, either through written instructions or with coaching by a Technical Service Representative, can likely save you that "out-of-box failure" experience and get your customer back in the air sooner.
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