Engine Oil to Alternator – The engine must be capable of supplying up to 2.0 GPM to the alternator. The alternator requires oil at the rate of 2.0 GPM at high speeds and 0.5 GPM during short idle periods, for proper cooling. A #5 line (¼ inch ID) or larger is recommended. The oil should be freshly filtered and as cool as possible. The alternator assembly includes a tee with a male ½-20 straight thread and an SAE 45° flare for attaching the engine oil line.
The original tee must be used for proper distribution of the oil. A small orifice is built into the tee to meter oil to the bearings, and the rectifier housing has a large orifice to control oil flow to the alternator. Use of a commercial tee without the small orifice will cause inadequate oil flow to the alternator, causing it to overheat resulting in short life.
Maximum allowable inlet oil temperature is 121°C (250°F). This includes severe operating conditions. Use of high quality oil with high-temperature protection additives is strongly recommended for maximum alternator life at this temperature.
Alternator Oil Drain – The oil drain line must have a continual downward negative slope to the engine sump and discharge above the oil level. Ideally the drain line slope should be constant to obtain “open channel flow” (oil flowing in the bottom of the line with air above). Deviations can result in “conduit flow” (part of the line filled with oil), which is less desirable.
Any low point along the line can cause the alternator to overheat and fail within minutes.
The drain line should have gradual bends with as few fittings as possible. All fittings should be #16 (1 inch ID).
A slot is provided in the stator lamination to drain the cooling oil that is in the end opposite the large drain hole. Also, the diodes in the rectifier housing need to be submerged in engine oil for proper cooling. Therefore, the alternator must be mounted to have the DC output terminal within 20° of vertical.
Vent Line Required – A vent line between the alternator stator frame and a continuous source of positive vent pressure such as the valve cover is required. Without the vent line, a vacuum is created in the alternator, which restricts oil drainage and will result in alternator overheating.
A female ¼-18 NPTF pipe thread is provided in the stator frame for vent line attachment. It is desirable to have the engine connecting point pressure approximately equal to crankcase pressure.
The line must not have any low spots because oil will collect from the oil vapors, blocking the air flow effectively closing the vent. A ¼ inch line is recommended.