A customer says their oil pressure light stays on all the time. What is the least likely cause? This video is sponsored by FRAM.
A. The pressure switch could be faulty.
B. The wiring between the pressure switch and the warning light could be grounded.
C. A faulty pressure regulating valve could be dumping all the oil back into the crankcase.
D. The oil filter is restricted or clogged.
The answer is D, the oil filter.
Oil filters have bypass valves that will allow oil to bypass the filter if it is clogged.
A and B are about the electrical operation of the light. The warning light is wired in series with an oil pressure switch. The pressure switch contains electrical contacts that are in a closed position when the oil pressure is below 5 PSI. When the engine is not running and the ignition switch is turned on, the warning light comes on. When the engine is started, oil pressure will compress the diaphragm in the pressure switch, opening the contacts and causing the light to go out. If the warning light remains on for more than one or two seconds after the engine has been started, shut it down immediately. Answer C covers a less common issue with the regulator valve for oil pressure. Sometimes the valve could be stuck open and not allow the engine to build oil pressure. In some cases, it could be stuck closed and excessive oil pressure could damage the engine and potentially the filter.