Info Solution for oil light 3ln3 into 3ln1 engine swap and vice versa

I have seen a few posts about people having issues with the oil light function not being correct when a later model engine with an oil pressure switch is fitted into a 3ln1 with an oil level switch and vice versa so I came up with a solution which inverts the operation of the switch. I havent tested it myself yet but it should work.

The problem is that a 3ln1 or earlier engine has an oil level switch. When the oil level is low the switch completes the circuit and turns on the oil light. The oil pressure switch on later engines works in reverse, when oil pressure is low the circuit is broken which acts as a trigger to turn on the light.

The solution if putting a later engine into a 3ln1 is to use a normally closed 4 pin relay with the trigger coil fed 12v when the ignition is on. You can tap into somewhere else in the bike that supplies 12v. I like to remove a spade from a connector block and fit a new one with an extra tail coming off it. It means not having to cut into the loom and compromising the insulation. Its also easily reversed.

The other side of the trigger coil goes to the oil pressure switch. The original feed to the pressure switch goes to one end of the switching side of the relay and the final pin on the relay goes to ground.

In operation when oil pressure is good the pressure switch completes a circuit which energises the coil in the relay and holds the other side open and breaks the circuit from the oil light on the clocks.

When oil pressure is low the trigger side of the relay has its circuit broken which allows the relay to close and provides a ground for the oil light circuit. And thats it.

If putting a 2kr or 3ln1 engine into a later bike the same circuit should work but this time use a normally open relay, (these are the most commonly sold ones)

Hope this is useful to some people.

 

Its simpler than it looks, and its good to have multiple options if you cant find a suitable replacement pressure switch.

Its also the only easy option I can think of if fitting an older engine with an oil level switch into a later bike.