Morris Minor Owners Club

I was driving on Monday and the oil light suddenly came on, I pulled in straight away and checked the oil level, which was fine and the engine sounded and pulled as normal as I only 1/4 mile left to get home I drove on. I only got around to looking at it again today. When you turn the ignition on there is no oil light on, then when you start it the oil light lights up. I have checked and cleaned the contacts, changed the switch for a new one and its still doing the same thing. I also turned the engine over when the switch was out to make sure nothing was blocking the switch.

Any ideas what to try next?

Ta

It's such a simple circuit that I can't think what could go wrong.

It is a switch that you've fitted, and not a sender for a pressure gauge I trust.

Well - it's wrong way round - the light should be ON when you first turn on the IGN - and then goes out when the oil pressure rises above 5 psi. Sure this isn't the 'blocked filter' warning light you are seeing ? Take the wire off the oil pressure switch and tuck it away so it can't touch anything - now try the engine - what do you see?

And while the wire is off the switch, also try shorting the wire direct to earth and check that the warning light does come on. It would be worth checking behind the speedo - there should be two lamps that glow through the orange lenses - make sure that both bulbs are OK.

Time to check the bleedin' obvious.
You have got the red ignition and orange oil warning lights in the correct positions?
Time to fit an oil pressure gauge

It wouldn't really matter - both should come ON with IGN - and go OFF when the engine starts..........

True, but you could be looking for an oil pressure problem instead of a dynamo problem.
Been there, seen it, done it!

Indeed - but the 'test' I suggested pulling the wire off the oil switch will soon tell!

I wont get looking for a couple of days as Im back to work, the green minor has been brought of of hibernation and put into use until I get it sorted.

As the engine sounded normal you have enough oil pressure.
The 4 psi that causes the light to come on is roughly equal to nothing, and the engine will sound like a bag of bottles, self destructing very shortly afterwards.

My 1275 engine runs at 30psi hot and the oil pressure light seems to operate at about 15psi and comes on at 30mph after a brisk drive. Listening out for the ends!

I wrapped up well this morning and ventured out to look at this again. I decided my best course of action was to take the one I knew was working out of the green minor and try it in the blue one. Problem solved! So this means that the new switch was also duff. Ive put it in the green minor as a temporary measure and its been parked up in the garage again out of the icy weather.

My modern minor (1969) is by far the best option for winter driving, fresh air heater, proper orange indicators and wipers that wipe in tandem even a heated back window