Hello, The oil light has always seemed to be a bit sporadic but at the moment I can’t get it to work at all when turning the ignition on. I’ve replaced the bulb, checked the connections and generally had a fiddle but now I’m just beat. Should I not drive it if I can’t get it to work? The wires are a mess in our van and tbh I’m not very electrically minded at all! Thanks in advance
Turn the ignition on, pull the lead off the oil pressure switch and dab the terminal on to the crankcase. The oil light should come on. That’s your starting point.
I would avoid driving the bus until you get the bulb to work, as you do not have long to turn off the engine when the light comes on when you run out of oil.
Thanks, if it comes on, it’s a faulty switch? And if that’s the case, is this the one to replace it with? It’s a type 4 engine. https://www.alanhschofield.com/ourparts/prod_2453850-VDO-Oil-Pressure-Switch-79-021919081.html (I know it says type 1 on there but when I’ve looked around it seems that’s the one)
Dodgy switch...or there’s no oil in the engine . Someone will confirm whether the switch is ok for a type 4. Don’t overtighten it!
...or if it doesn’t come on and you’ve changed the bulb, could be a fault/break on the wiring or on the back of the instrument pod.
The oil pressure switch and light is basically tested by the fact that the switch contacts should be closed with no oil pressure, which is the case after a while when the engine stops. So when you turn the key you get the alternator and oil pressure warning. Start cranking and the oil light should go out after a couple of seconds, when the oil pressure has reached about 4PSI/ 0.25 bar. Once the engine fires and has passed the alternator cutoff speed, the alternator light should go off and stay off. The alternator light might not go off if the engine starts and idles immediately when the choke is warm, but it will go off if you rev the engine a little, then it should stay off. If either light comes on solid once the ignition is on, either the engine has stopped, or If the alternator light is on, the fan belt may have fallen off, which is serious for overheating reasons. You have a minute or so before the engine really overheats so pull over and switch off. So then you check in the back for the belt, if its still there, the engine will run off the battery to get you somewhere you can look at the alternator and its wiring. If the oil light comes on solid, stop the engine, pull over in neutral, you have seconds before the engine is damaged in the worst case. The difference is that when the fanbelt breaks, the engine was being cooled OK, then it starts heating up. People run drag races in beetles generating much more horsepower, with the fanbelt disconnected for maybe a minute or so. When the oil light comes on at normal engine speed, you are at the end of the failure story where the oil pressure has been dropping for a while, and now it is just about to stop lubricating the bearings, either because the pump is pumping air, or the engine is hot and/or worn out.
This is fantastic thank you. I think when I first got it, I didn’t realise the oil light and alternator should come on when you turn the ignition but it’s something I always look for now. One question, if you had already driven for, let’s say 30 mins, and then stopped and turned the ignition on again within 5 mins, would the oil light not come on because the pressure is already higher? If that’s correct, how long does it take for it to be expected that it comes on again?
Oil pressure will drop shortly after turning the engine off, as the oil pump is no longer running. The light should come on every time you turn the ignition on, then go out after the engine is started.
Thanks. I ordered a new switch as it pushed me above free postage on Schofield’s anyway, so I will have a proper look soon and probably come back on here if I can’t get it to work! edit to add: anyone got any guides to changing the fan belt? And how do you know if it needs changing?
Yes. Cool, I wasn’t sure if there are warning signs, it always looks like it’s bobbing up and down quite a lot but maybe that’s just how they are!
The belt shouldn’t ‘bob up and down’ more than 10mm. If you don’t have a Bentley or Haynes manual (and you should), this might help https://thelatebay.com/index.php?threads/procedure-for-tightening-alternator-belt-type-4.54087/
Sometimes the fan/pully assembly is dismantled to clean and paint. If not put carefully back together the fan and pully are unlikely to be concentric and the pully will wobble causing the belt to bob up and down. Have a look when it's running.
