I have a 150 mark IV that the oil pressure light has been coming on sometimes,we replaced the sender but that did not help.Then we put in a mechanical pressure gauge, when the light came on it was still in the 40 on idle to 75 full throttle pressure range.Local dealer said 75 was to high that it should not top 50 , so we cleaned the pressure relief but it was fine.He also said it could be a wire shorting out.We tried to check that out , one wire is grounded and the other has 24 volts to it so I don't understand how that can be it.If on the hot side I thought it would blow a fuse and if short on ground side , what if it rubbed cause its already grounded.I don't know if its a computer thing or how to find it or a broken wire with out knowing where to start on other end.The mechanical gauge says all is well so I feel as we are chasing a ghost.Any good ideas? It has a cummins motor that runs fine.
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150 kobelco mark iv oil pressure light
- Thread starter adigger
- Start date
TraxnTrux
New Member
OK, indicator lights work off of switches. Gauges use sensors. (variable switch). You have voltage (hot) going to the gauge. Operation depends on the wire being grounded by the switch. ANY circuit that is in operation will show hot at an unconnected ground point. If you ground the "hot" wire at the switch the light will come on. You probably have a wire from the light rubbing somewhere before the switch. This will complete the circuit and illuminate the light. Unhook the wires at the switch and tape them up temporarily. If the light comes on it is definately shorted to ground. This could also be a panel issue where the wire to the switch is being grounded. The fuse wont blow unless grounded before the light. Anywhere else just completes the circuit and illuminates the light. Hope this helps.
TraxnTrux
New Member
Everything after the light is actually on the "ground" side of the circuit.
oil pressure
My problem with it is the dealer says 50 pound pressure is the high and we are running 80 to 90 at top even after cleaning relief valve according to the mechanical gauge we put in.Why / How do we get it down?
Everything after the light is actually on the "ground" side of the circuit.
My problem with it is the dealer says 50 pound pressure is the high and we are running 80 to 90 at top even after cleaning relief valve according to the mechanical gauge we put in.Why / How do we get it down?