Oil pressure warning lamp

[d.man]

Hi all - am now the proud owner of a 1994 m900 :)
I have a puzzling problem with the oil pressure light on the dash - it does not illuminate.
Bulb is fine (double checked that with one that did), no fuses blown and if I touch the terminal on the crank case (a la Haynes manual) the light does not illuminate.
Is the oil pressure switch definitely broken?

Any ideas/advice gratefully received

Thanks all

[Mr Gazza]

All the switch does is make or break the earth connection, so it may well be working as your light does not come on when you bypass the switch by earthing it.

Two things could be wrong here. Either the earth connection of the engine to the frame has failed...Unlikely but has been known.
Or more likely is that there is a break in the live wire going to the bulb. Not easy to find, as they break the wire inside and only leave a very subtle witness on the insulation if at all.

You might be able to find a break, most probably where the harness flexes with the handlebar movement, but probably quicker to do a continuity test then just splice in a new cable if needed.

[Mr Gazza]

Been worried sick all night about what I posted..:dizzy:

I am fairly sure that the bulb gets it's live feed from a short wire within the dash which also feeds the other bulbs.

So much more likely to be the black (earth) cable that runs to the switch, but otherwise, as above.

[d.man]

Hi Mr Gazza - appreciate your reply and advice.
I'll have a good look at wiring and see if I can find a problem.

Will let you know how it goes.

Cheers
Danny

[pompone]

If you unplug and short the wiring harness end, and the light goes off yes, the pressure switch is at fault.

[d.man]

If anyone can give me an idiots guide to checking continuity - I'd be grateful.
I have a multi meter - but electrics are in no way my forte (am confused by all the settings!).
Again - any help gratefully received

Cheers
Danny

[pompone]

Look for either a diode-like sign or sound sign. Put one terminal at one end and the other at the other end. If you have the right (or non broken wire) it will make a sound (or show a number, usually a 1 on the lcd) if nothing happens you have a broken wire. there are plenty of articles out there, just not easy to explain without writing loads.. ;) but is really simple stuff..

[d.man]

Am now very baffled:
Using a blue peter style set up with batteries, wire and a bulb I, having disconnected the speedo housing at the multi pin connector, have-
Connected my wire to the relevant pin and the other end of my wire to the spade end (pressure switch) connector - there was light.
In the speedo housing connected my wire to the correct socket at the multi pin connector and the other end of my wire to the yellow/white connector - there was light
Put power through the multi pin plug to power the yellow/white and blue wires - there was light

All wires seem ok to me - but if on switching on the ignition or if I earth the spade end connector to crank case - nothing

Help!!

[Mr Gazza]

Do you know if the dash lights are getting power?
Do your indicator repeaters and high beam warning lights all work? (with the ignition on)

I wondered if the paint on the crankcases is preventing an earth...Try touching the spade onto a bare bolt head or better still, if it will reach, onto the negative terminal of the battery. (with ign on).

If you have all the correct continuity it could be a poor connection in the multi pin connector?

To narrow it down a bit more....If you can get to the warning light bulb holder with the multipin still connected. then jump the negative terminal on the holder to a good earth with your test cable.
With ignition on, if the warning light comes on it would prove a live feed all the way to the bulb.
If not, use a test bulb and wire from the positive of the holder to earth. no light means no live to the holder. light would mean bulb not making contact in the holder (Or duff bulb).

Don't give up...:mand:..You've already earned a Blue Peter Badge...:chuckle:

[d.man]

Thanks for the advice - will try that when I get home later.
Showing my ignorance for all things electrical now; but if the bike is on rear paddock stand, w

[d.man]

Thanks for the advice - will try that when I get home later.
Showing my ignorance for all things electrical now; but if the bike is on rear paddock stand, would this affect earthing?

[Darren69]

No it only needs to connect to the battery negative terminal to complete a circuit/be earthed. The bike should already be connected to the negative terminal by means of the earth strap on the crank case behind the rear cylinder. I think if that were faulty you wouldn't get any power at all, as I think most circuits use that.

[d.man]

Success - of a sort.
Identified that power was going to the bulb and wiring is ok.
Decided to check all earth points and clean them up.

Still no light on dash, but when I uncoupled wiring from pressure switch and earthed to a frame bolt (cheers for the idea Gasa) - the dash light came on.

A new pressure switch it is then!!

Thanks to all for their help - hugely appreciated

Danny

[Mr Gazza]

That's very good progress.. Well done.

I just wonder if you can get the same result by touching the wire on an engine case bolt? To prove that the engine is electrically connected to the frame.?

In my experience it is unusual for an oil pressure switch to fail leaving the light off. Mine have always gone leaving the light on..Or flashing on intermitently with the engine running.

[d.man]

Just to let you know - new oil pressure switch has rectified the problem:)
Again thanks for all the help
Danny