1991 750SS, lovely bike, but fickle. It only has 8300 miles from new but it has more than its share of 'character'. I last rode it about three or four weeks ago and all was well, but today when I fired it up the oil warning light stayed on. Oil level is at the top line, the oil and filter were replaced 200 miles ago. The oil strainer is completely clear of debris. I removed the pressure switch and turned the starter and got a healthy pump of oil out. I removed the wire from the switch, the light went out, I earthed the wire, light on, so the wiring is fine. the switch itself has continuity through it when contact is made by pushing against the internals to activate it with a probe - I can feel the movement inside when I push against it. I'm guessing it is a captive ball bearing that oil pressure forces up to make contact in order to extinguish the warning light. I primed where the switch sits with oil when I put it back in. When I run the engine (briefly) and blipped the throttle, the light stays on. I'm hoping that the switch for some reason now needs more pressure to activate it than the oil pump can provide, and the replacement switch on order will cure the fault. I'll let you know - feel free to chip in with thoughts
I have had these fail by letting oil through to where the wire goes. They are cheap if you get pattern ones, about £40 from Ducati
Had two fail last month on two different bikes. Now bought two oil gallery plugs to cure once and for all. 2 quid each.
For My 900ss I used to get Vauxhall oil switch , it’s the same as Ducati for about £4. 750ss switch likely to be the same as 900 so try Général Motor factors for a cheaper part.
So you think it is only the switch then? The early 750 had a different wiring connector judging by what it says in the Haynes, I'll see what the one I have ordered looks like. It is an upgrade part - the original part number has been superceded, so I suspect I'm going to have to tweak it. I don't suppose you have a part number of the Vauxhall one do you? This sort of thing always happens when you have a couple of spare hours and the sun is shining, doesn't it?
you can find details in the "Alternative parts" thread somewhere on the Forum and i have linked same around 3 times this year.
Mine looks more like the VW alternative, with the exposed blade connector.... https://www.ducatiforum.co.uk/threads/alternatives-to-the-genuine-ducati-parts.594/ https://www.ebay.co.uk/itm/Oil-Pres...9081D-68919081-68919081D-1669964/233587389632
You could always invest in a oil pressure gauge with a short hose and a adapter and test with that. I found mine really handy on so many occasions
If it's a spade connector I used the pressure switch from my TR6 (car) till I got another one I have a short lead made up so I can use either type of connectir
The older bikes, like the OP's, have a switch with a spade connector and 10mm x 1mm pitch thread. It is the same as used on many VWs. Later bikes use the Vauxhall type.
I'm guessing all these alternative oil pressure switches operate at the same sort of oil pressure as the Ducati's operate at ? I know it's a different bike, but my '76 Kawasaki has a very low oil pressure, standard oil pressure is 2.8Lbs/sq.in. so you'd need to be careful when selecting alternative switches. Both my children started their driving careers with Vauxhall Corsa's & these had issues with the oil pressure switches failing, (oil leaked from the electrical connection on top of the switch body) but they had changed the design of them when I bought replacements, which in fairness will have been around 8 years ago.
I think they are usually around 3 or 4 psi but if the oil pressure is as low as that there is a serious problem anyway.
Oh right, quite a common "switching" pressure then ! The Kawasaki is that low because it has a roller bearing crank & these type bearing can't hold pressure like shell bearings do. Although the early Kawasaki cams run in shell bearings the standard oil pressure for the Z1's is still very low, seems to work though !
Maybe nothing, but I used to have a 1993 900ss and lent it to my father, as he was the one who got me into Ducatis. He topped up the oil while on the side stand and obviously overfilled it. I picked the bike up and saw the oil light flicker on, when under acceleration, so assumed it was low, but it was way over the limit. Oil syphoned out to the correct level when upright and it sorted itself. Thankfully, no damage done.
I think you are right, as logically this must have been a "good" sender when first designed and fitted in it's tens of thousands,but something fairly fundamental has been altered to change this, it could even be as simple as a change of plastic spec.
Ok, so a bit of further news, I have received the new Ducati replacement switch, and put on the bike to test it by putting a wire on crocodiles across from the bike to the switch as a temporary measure. The warning light extinguished instantly on startup so I know the original fault was purely a failed switch. The replacemement part number from Ducati is a switch with a black/yellow waterproof connector, not a male blade connector as per the original part fitted to my 1991 750SS. The VW/Audi group switch available freely on Amazon and Ebay, a FEBI 08484 switch, has been ordered because it has a blade connector as per the Ducati part fitted in 91. The original switch on the bike has markings on it that say it switches at 0.8bar to 1.2 bar, the VW one is 1.2bar to 1.5 bar. Provided the VW switch extinguishes the warning light on startup, I'll be happy to leave it on the bike as it tells me that pressure from the pump is good. It also means I won't have to change the connector on the bike to suit the replacement part number switch. I don't want to do that becuase the bike is original front to back with only 8000 mile from new and I want to keep it that way. The VW part is ordered, and will be delivered tomorrow. I'll post the findings in due course.
