![]() ![]() If not, check the regulator and associated connections, conductors, breakers, and switches.Ģ. While the engine is not running, verify field (F1) input voltage, which should be the approximate bus voltage. If there is no tug, then the alternator may well be working correctly and the problem could be a faulty voltage regulator, wiring, or an alternator field circuit, which leads to several other troubleshooting steps to help identify the issue:ġ. Failure of either of these tests would be cause to remove the alternator. If that does check out OK, switch the VOM to AC volts and verify a maximum of 1 volt AC into the bus. For 12- or 24-volt systems, if this is less than 13.5 or 25.5 volts respectively, when above 1,500 rpm, the alternator output is low. To do this, run the engine with the typical electrical load, connect a VOM to the B+ terminal and measure the voltage with respect to the ground. Energizing the aircraft’s alternator circuit while the unit is not running creates an electromagnet, so when you hold the scale against the housing you will get a light magnetic “tug”.īut, even if there is a tug you still need to verify that the aircraft’s alternator can carry a load. Next, with the aircraft’s Master and Alternator switches both on, place the metal scale on the alternator chassis. The first step is to switch on the aircraft’s Master and use the VOM to record the DC bus voltage for further troubleshooting reference. You can find it at: Alternator Troubleshooting TipsĪs you will see in the video, an experienced mechanic can perform 95 percent of the steps to troubleshoot a piston-engine aircraft’s alternator using a flexible steel scale (not stainless) and a calibrated Volt/Ohm Meter (VOM). So if there’s a charging system issue, complete the following basic troubleshooting steps to the entire system before removing the aircraft’s alternator.Įven before they go out to the customer’s airplane, the first thing I tell technicians to do is to go to HET’s website and watch our short video on electrical system troubleshooting. Unfortunately, any of these issues will often lead to a “failure” indication. There are a number of things, which may look like alternator problems that aren’t. The real issue could well be something else under the cowling. ![]() Keep in mind that just because the alternator went off line, it doesn’t mean the aircraft’s alternator itself has failed. The problem is simply that not enough troubleshooting was done before pulling the alternator off the airplane. ![]() But, in many cases, when we bench test these “failed” alternators we find that they’re actually working fine. Many times, at least according to the technician’s diagnosis, the problem stems from a faulty alternator - especially if the pilot sees that little red light in the panel light up. Aging wiring, connectors, batteries, and issues with other components can play havoc on not only the system’s performance, but also a technician’s ability to find and fix a problem.Īs the director of product support for Hartzell Engine Technologies (HET), hardly a day goes by where we don’t get a call or email from a technician needing help weeding the gremlins out from under a customer’s cowling. The electrical system of a piston-engine airplane may seem simple enough, but therein lays the problem – it’s not. ![]()
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