Oil pressure sending unit.

[Joe Rocket]

This old GPX continues to throw up niggling problems. This time the oil pressure light randomly flashes. This has come about since I found a weep of oil from the clutch cover. A new gasket and remedy for the slight step in crankcase halves and that's now sealed and fine. It was the last oil refill that showed the oil pressure light problem. Note please that I've triple checked the oil level!

I have good old Haynes but there's a contradiction in the manual's explantion of checking the fault.

Here's the text directions:  ".......disconnect the wire from the oil pressure sending unit. Turn the main switch On and earth the end of the wire (see illustration). If the light comes on the oil pressure sending unit is defective and must be replaced.........". 

I did that and the light came on.

Here's the illustration instructions: "When the ignition is On and the wire to the oil pressure sending unit is earthed the warning light should come on". 

The statement doesn't conclude it's a faulty unit!

If anyone knows can they confirm the correct fault diagnosis please.

This has been a mammoth task as the bike has had to be stripped down including fairings, radiator, oil cooler and exhausts just to access the wire on the pressure sending unit. I'd like to only have to do this once.

Thanks in advance for positive advice, as usual.

[kwackboy]

If it's just a single wire, In my opinion, the second is correct.

The circuit is being made by earthing the wire eluminating the light which is testing the circuit not the switch.

You should be able to test the switch by removing it and putting a meter across it .

[Mr Nick]

The oil pressure should hold the contacts open against a spring so the circuit connects when it drops: better fail to safe option that way.

I think what the first is saying is that, if the oil light doesn't come on with the ignition, then earth the wire to check the light does come on - if it does then the switch has failed. If it still doesn't, check the bulb.

[Joe Rocket]

Okay, I see the sense in how the two situations are in fact the same.

The light comes on, the circuit is sound therefore the 'switch' is at fault.

Thanks to both Kwackboy and Mr Nick.....as usual. 

[Mr Nick]

It may well be that the internals of the switch have come apart & not being fully 'pressed' by the oil. The way to be sure is to put a pressure gauge in the switch feed to make sure that the pressure isn't fluctuating causing the intermittent light. If you don't have one, then swapping the switch & hope is what you're left with.

[Joe Rocket]

That seems likely as the rest of the circuit is complete. I don't have air/guage to play with the switch but it will be awkward to get a spanner on it to get it out. The manual says "just earth the wire to test it" and "drain the oil to change it for a new one".........  I struggled to touch it with my finger through the centrestand and exhaust! 

Yep, a new switch and hope that's the cure. Thanks Mr Nick.

[Joe Rocket]

I'm having a lot of bother with this switch. It is awkwardly placed although I have full sight of it. My standard tools end at around 22mm for sockets and spanners apart from a couple of 'used it once' specials. I measured the switch body at 24mm and bought today an open ended and ring spanner. The open ender only fits end on to the unit, impossible to get a normal fit as there''s too much too close. The ring 'fits' but the unit hex body has rounded corners so 12 point spanners and sockets won't work. There is also only 2cm clearance between the frame support for the uni-trak linkage and centrestand. (The bike is on the sidestand with e centrestand out of the way) Other parts obstruct access to get a spanner on this.

In short I need a dumpy six sided socket and hope there's enough space to get a 3/8 or 1/2 drive bar on it.

So why is this causing so much hassle? Quite simply the manual was written and this item covered when the engine was out of the frame! An assumption was then made that you only have to drain the oil, undo the old unit, screw in the new and replace the oil. In my first post I listed how much I've had to strip the bike down and now I find a 'bastard' hex body on he switch. Not a happy bunny. 

[V-Twin]

Welcome to the life of a mechanic.   

[kwackboy]

 

If I was in that situation and I didn't have a tool, I'd make something to get me out of trouble.   

[Joe Rocket]

I get the point. If I had welding kit, a lathe, a milling machine etc. I'd do it too. (Funnily I do with wood as that's my background)

I have the option of dropping the sump to which it's bolted. So it's buy a socket or two to find out or new sump gasket at least, plus the garage floor level hassle. It might end up both yet! 

[Rusty Nuts]

A theoretically replaceable yet practically inaccessible part. Much fun.