Oil Pressure

I have a 1995 Super Custom.
The oil light comes on when idling and hot.
Under pressure it goes off and is off when starting.

I fitted a new oil pressure switch and same happens.
A mechanic suggested changing the filter which I did but no better.

Any suggestions? Thanks

Could be wrong grade oil I put 5/30 in a 1kzte it rattled like mad took it out used 10/40 perfect.

Thanks. I use 10/40 as it is an old engine.

Good Morning John.

That motor can have a minimum 4.2 psi cold and over 36 when under load. The light is set around 5.

Things to rule out:
-Wrong filter without anti-drainback valve: you report no cold starting pressure issues so that looks good to me.
-Sensor failing: you replaced so good to go.
-Wrong oil viscosity: all things considered it should make pressure with straight 10 weight, so although there is completely a right oil for the engine, the wrong oil shouldn’t go below 4.2 psi.
-Low oil can cause this problem but you just changed it so cross that out too.

When the oil warms up pressure falls. How far yours is falling we truly don’t know. Next step is a manual gauge rest to verify you don’t have something mechanical going on. It’s easy to handle yourself. Everything else is just guessing at the moment.  Toyota publishes online how to do this test and I would definitely run it as soon as feasible so you can continue to enjoy your van for many years to come.

Please message me to call if you have any questions or issues. I hope you get this fixed soon.

-Bryan.

Well thank you very much Bryan for your kind advice.
It is good to know I can message you if I need to.
I have done most of what you suggest but I will investigate further.
It runs and starts very well !!