Oil pressure light

Technical Big Block Tonti and Loop Frame models
1

Hello
Just started my T3 and the oil pressure light isn’t going out. I changed the oil just after the last run (about 6 weeks ago) and haven’t started it since. I’m guessing the oil pressure switch is faulty which looks straight forward to change but any other ideas (pressure relief valve?). Just don’t tell me I need a new oil pump please :astonished:

Thanks in advance for any help.

Rich

2

:bulb: With the ignition on and engine not running.
Take the wire off the switch and touch it onto the engine case.
If the oil light works then the switch has failed.
Easy job to replace.
Good luck
Steve

3

It should go out when you disconnect it from the sensor and come on when you touch it onto the engine.

4

Hi
Looks like your advice so far contradicts each other?

If it’s a normally closed switch (i.e. opens when up to pressure and light goes out) then I think disconnecting the wire will switch off the light then earthing the wire to the engine should light up the warning lamp again? The way I see it this still doesn’t tell me if the switch has failed or more importantly if the oil is up to pressure. Or am I missing something?..
Maybe I should just change the (quite cheap) switch anyway and see what happens.

Rich

5

Yes it’s a normally closed switch. Oil pressure opens the contacts. But they can go wrong and stop opening.

I’m slightly worried tho that this is happening only just after an oil change… i.e. you did something to it … did you change cartridge filter as well?

Could be just coincidence.

I suppose you could do something like loosen one of the rocker supply hose banjos with engine idling to prove whether or not there is any actual oil pressure. Never done this tho (and would be a mite messy).

6

Afterthought: check the wiring in case something has gone awry so the wire has got a short to ground somewhere.

7

It is a single wire to the switch, so it must just be a switch to earth to complete the circuit. When the engine is not running, the switch is closed and allows the current to flow, hence the warning light illuminates,
When the engine is running, the pressure opens the switch and breaks the circuit, hence the light goes out.
I hope this explains it.

8

Don is correct. The switch is by now about a Pavarotti so no big deal.
Do not buy a cheap Intermotor replacement as they only lasted months in my recollection.

9

How long did you run it with the oil light on? If you fitted a new oil filter then it takes longer for the oil to circulate the first time before the light goes out.

10

You’re right.
I must have been having a grey moment :astonished:
All the best
Steve

11

Mia culpa!
A(nother) grey moment!
Steve

12

Not that long. :smiley:

Waiting on Guzzi-Rich to reply…

13

Yep understand thanks. Will probably buy one from Gutsibits and as you say they’re about a tenner.

14

Ran it for about 2 mins ticking over then switched off to investigate e.g. shorted wire, oil level etc. Then ran up the road about 200 meters and back still no good so didn’t risk any more.
Didn’t fit a new oil filter this time just an oil change so should still be a full filter of oil and some in the system. I suppose there could be an airlock but never heard of that before.

15

Thanks for all the help guys I’ll fit a new switch at the weekend and let you know how it goes

16

OK, just that if sump was off always a chance gasket was damaged when put back, so either creating an internal leak from a pressure gallery, or even blocking one, or cartridge not tightened. But one hopes one double-checks these things. :smiley:

17

Well I changed the switch today and light still stays on. Not running it for too long just in case but at a fast tickover for about a minute before I bottle it and switch off.

Bit puzzled as I’ve had the bike about 10 years now and done an oil change every year and never had this problem. This was just an oil change so didn’t change the filter and the sump didn’t come off. Definitely ok before the oil change.

Anybody seen anything similar before? I’m starting to get a dread feeling about the oil pump?

Rich

18

Unlikely to be the pump,
sounds like a short in the wire from the warning light to the switch
Phil

19

Hi

Light goes out when I take off the wire to the switch so don’t think it’s shorting to earth.

20

It might be an idea to loosen one of the oil feed banjos to the cylinder head and turn it over on the starter, with the kill switch off, see if any oil comes out.