1/13/2024 0 Comments 24 volt alternator voltage![]() These codes can lead to a faster and more accurate diagnosis. This is why a scan tool is essential to diagnosing a charging system. The battery light on modern vehicles, however, is controlled by data and trouble codes. On older vehicles, the battery light would turn on the alternator light when the alternator output or battery voltage dropped below a preset value. The other critical tool to effectively diagnose an alternator is a scan tool. Take time to look at the service information. This might also cause you to overlook critical problems. Not knowing what controls what, and how it is supposed to function, can cause a misdiagnosis. Some systems might even stop charging if an extreme load is detected and set a code. Ll not be able to keep up with the load when idling, and the lack of cooling compounds the problem even further. In most cases of undercharging, the alternator may have an incorrect diameter pulley installed, the drive belt may be slipping or the alternator itself might be under capacity for the vehicle application.Īlthough load-testing an alternator provides a quick way to test for drive belt slippage, keep in mind that an alternator can easily be overheated when testing for maximum output during low-speed operation for an extended period. Consequently, if the alternator doesn’t maintain rated charging voltage at lower engine speeds, the battery will discharge under heavy accessory loads. Many modern engines operate well under 2,000 rpm until they reach highway speeds of about 60 to 70 mph. This is why the ambient and underhood temperatures are critical data for the charging system.Īnother factor determining battery voltages are automatic transmissions with five or six speeds that can drastically reduce engine speed when cruising. The actual charging voltage designed into a voltage regulator is dependent upon factors such as how far the alternator is located from the battery and the ambient air temperature surrounding the battery as calculated by the PCM. Alternator output is on demand when there are loads detected or the battery needs to be charged.ĭepending on ambient temperature, charging voltage varies. ![]() This means that load on the engine is controlled to reduce parasitic loss at the crankshaft. This wide discrepancy in voltages is due to the fact most alternators are controlled by the ECM or PCM to improve fuel economy. Still, it’s perfectly normal for others to see the alternator not charge at all intermittently. For others, it’s normal to see as high as 16 volts for long stretches. For some, a constant 13.6 volts is an indication of a problem. If this is the case, it only means that the alternator is not charging, but does not reveal why.įor some alternators, it’s normal to see as low as 13 volts. All too often, the alternator is condemned as the source of the problem if only battery voltage is present with the engine running. O ne test is not enough if you are diagnosing a charging system problem.
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