I have a couple of Rover V8 oil pumps complete with seemingly a endless number of sender/sensors. I have bought a new oil pressure sensor (shockingly unlocost) and pressure relief valve/spring. There are several other senders that I think are oil pressure light and oil temp. If I have a working sender I might as well put a warning light on the dash. How do I test a pressure sender out of the vehicle?????

There is a difference between a sender and a switch, a sender varies it's resistance with pressure/temperature and is used with a gauge to give a progressive reading whereas a switch is either open or closed and is normally used with a bulb.

If you have a compressor with a regulator and gauge then you could use that to function pressure switches/senders and then just use a multimeter (set to ohms) to see whether it's a sender or a switch and what pressure the switch opens / closes at. You could also use a foot pump.

Temp switches can be functioned in a pan / kettle along with a thermometer and multimeter.

Cheers
Davie

Bike/foot pump and a multi-meter.