1979 R80 : is the oil pressure switch normally open or normally closed?

Northern Monkey

Northern Monkey

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just a very quick question, i have finally started up the bike after 18 months of tinkering but the oil pressure light is on all the time. i could do with ruling out the basics first if possible .

Ive heard that if the oil filter isn't in right that can cause a similar issue? but don't fancy dropping the oil to check so i could do with knowing how to test the pressure switch, should it be normally open and closes with pressure or should it be a closed circuit that opens once pressure is detected?

thanks:beerjug:
 
No idea. :rolleyes: :blast
But,
my 1980 R80/7 would often, after being left idle for a few weeks keep its oil light on for a good few seconds after start up.
Hope that helps. :nenau

EDIT:
i assembled the filter wrong one time - leant the Bike over on its left side - put it right - no oil loss.
 
oil pressure switch is normally closed. it puts an earth on one side of the oil pressure lamp causing it to illuminate.

when the engine starts, oil pressure rises and contacts open - lamp goes out.
 
just tried it now, full continuity from spade to earth, and no difference when i blow it, i'm assuming the pressure required isn't that much that i cannot replicate it. a new switch isnt that much and worth a punt :)

thanks
 
These switches do fail..and as you know, an easy replacement :-) If disconnected and wire earthed, then light stays on...if connected up and light stays on then it is the switch.

Most of the filter problems is folklore passed on from website to website. Beside the very early /5 etc models...only two types of filter required...long or hinged/with or without oil cooler ! I always use a paper gasket and a new white oil 'O' ring ( every two or three changes ) ...never had a problem in 35 years :-)
 
aaaaaaaaarrrrrrrrrrrrrrggggggggghhhhhhhhhhhhhhhhhh h

I hate to resurrect an oldish thread but im about to set fire to the fecking thing!

i rearranged the oil filter and replaced the pressure switch, i tried it and the light was out, all gravy i thought. so i moved on to the rest of the snag list.

i started it up today with jump leads ( the battery is knackered and needs replacing ,granted its been stood for a while ) and the oil light never went off. WTF am i missing here?

the only work to the engine was to the heads, i haven't touched the bottom end and it was 'fine' before i started fooking around with it many years ago!

if all else fails i may have to admit defeat and just strip for bits.

the following options have been ruled out on grounds of being poor a) buy new engine, b) pay someone who knows how to fix it, c) just feck it and go and live in the bahamas.

any help no matter how stupid it may seem to you may very well just do it! :)
 
I think I would put an oil pressure gauge on it (you can use the oil pressure switch take off) and measure whether you actually do have pressure or not, rather than speculating at this stage.

Once you have go tthe basics covered, work up from there.

i.e

is there oil in the sump to the correct level?

Is there pressure when measured?
 
I borrowed a pressure gauge ...... At idle it's 10psi and goes up to 30-35psi at around 3000rpm is that good bad or indifferent???


Sent by magic
 
I dont know off hand what the pressure specs are for the airhead engine (lower than you might think probably) but the main purpose of the exercise was to see if you had pressure or not, which you do, so the warning light should extinguish. On the face of it it sounds like either a switch or wiring issue.

In my earlier mechaninc days it wasnt totaly uncommon to fit a new part out of a box, only to have it fail unexpectedly very quickly.
 
solidstate100 said:
...
In my earlier mechaninc days it wasnt totaly uncommon to fit a new part out of a box, only to have it fail unexpectedly very quickly.
Click to expand...
So you go through every other damn thing it might be, before coming back to the "new" part - scratching your head thinking "it cant possibly be ____, coz that's brand new!" :confused: :rolleyes:
yeah - been there too. :banghead:
 
Northern Monkey said:
I borrowed a pressure gauge ...... At idle it's 10psi and goes up to 30-35psi at around 3000rpm is that good bad or indifferent???


Sent by magic
Click to expand...

I think those pressures are a bit on the low side, a freshly built engine is capable of 160psi when started cold and would run at 80 to 100psi when warm.
 
the switch should work around 7psi. Are you sure the connector under the left hand side panel hasn't come adrift or broken?

If you pull the side panel theres a 2 core cable that has a brown wire with a green tracer and a brown wire with a black tracer. unplug the cable and use a piece of wire to short the brown/green cable to earth. If the oil lamp comes on then the circuits good from the lamp. obviously the oil lamp should go out when the wire breaks.

The other thing...Based on another new airhead rider on this forum who came round to mine (and shall remain nameless) are you sure you are looking at the oil light on the dash? they can be confusing. the fella in question alternator wasn't charging and he'd got the lamps mixed up. The oil is the 2nd lamp from the top.
 
Northern Monkey said:
I hate to resurrect an oldish thread but im about to set fire to the fecking thing!

i rearranged the oil filter and replaced the pressure switch, i tried it and the light was out, all gravy i thought. so i moved on to the rest of the snag list.

i started it up today with jump leads ( the battery is knackered and needs replacing ,granted its been stood for a while ) and the oil light never went off. WTF am i missing here?
Click to expand...

ok, i'm slightly confused here.

you say the light was out. was this with the ignition on?

then you say the oil light never went out. at what point did it come on? i'm guessing when you started the engine. here's what i would do...

ignition off - lamp should be off

ignition on - lamp should be on

start the engine - lamp should go out. if it doesn't, it's either low pressure (unlikely), sender/lamp wiring shorting to earth (possible, but still not very likely) or a stuck switch in the sender (much more likely). easiest thing to do is swap the sender for a new one.





Northern Monkey said:
borrowed a pressure gauge ...... At idle it's 10psi and goes up to 30-35psi at around 3000rpm is that good bad or indifferent???
Click to expand...

i can't tell you offhand what the oil pressure should be, but i'm pretty certain that the sender switch should open at very low pressure, say less than 5 to 10psi.
 
When engine was running after restoring , oil light ( Amber) stayed on and did not extinguish as it should.

I dropped oil , rejigged the oil filter and bought new sender - started engine and the amber light was extinguished when engine was running

- I thought I had solved the problem but when started after stood for a month the Amber light would not go out when engine running.

Does that make sense??


Sent by magic
 
Arkwright said:
I think those pressures are a bit on the low side, a freshly built engine is capable of 160psi when started cold and would run at 80 to 100psi when warm.
Click to expand...

Cut and pasted below is the text (allgedly official figures) from Snowbums site for the Airheads re oil pressure:-

"NOTE: The oil pressure warning lamp switch is NOT at this part of the left side galley I mentioned above. Rather, that switch is located in a different part of the oiling system...MUCH farther down the line, actually in the galley that supplies the rear main bearing. The pressure in the switch area is about 14.5-29 psi at 800-1000 rpm; and about 60-74 psi at 4000 rpm. These are official figures, and will vary rather a lot (higher, especially) with oil temperature, type, and grade. That switch has threads of 12 x 1.5 mm. NOTE that very early airheads had a 3/8 NPT thread. ...also note that the later switch is the same as mid-seventies 2002 BMW car sender."

So on that basis, yes perhaps a little low, but probably commensurate with its wear. That said (as Rob has confirmed) the switch operates at around 7psi so should still extinguish the light. Not sure where Arkwright gets the very high figures from, particulary the idle one, as the pressure relief valve should operate at around 75 psi (according to Snowbum) to peg back the high pressure when cold, as this can damage the engine.
 
Northern Monkey said:
after stood for a month the Amber light would not go out when engine running.




Sent by magic
Click to expand...

My guess is a stuck switch - as we have established there is oil pressure. Not uncommon for things to "stick" when unused...........

Also, isnt the oil light red, not amber (which is the indicators colour........?)
 
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