BMC A Series oil warning light
 

On to the next little problem - oil pressure warning light always on. I
fitted a new pressure switch a while ago, which made no difference so
checked today, and found that the light is on (with ignition) even when
the wire to the sender is disconnected. Inspected the loom, with no
obvious damage, which suggests a short to earth somewhere in the rat's
nest behind the speedo. Bugger.

Being a late (68) model, there are two yellow oil warning lights, one
for low pressure and the other showing clogged filter. I have never
seen the clogged filter one lit in 22 years, so tested it by shorting
the connection to earth, and it works.

Oh well, out with the speedo.
--
Graeme

BMC A Series oil warning light
 

Graeme Wrote in message:

On to the next little problem - oil pressure warning light always on. I
fitted a new pressure switch a while ago, which made no difference so
checked today, and found that the light is on (with ignition) even when
the wire to the sender is disconnected. Inspected the loom, with no
obvious damage, which suggests a short to earth somewhere in the rat's
nest behind the speedo. Bugger.

Being a late (68) model, there are two yellow oil warning lights, one
for low pressure and the other showing clogged filter. I have never
seen the clogged filter one lit in 22 years, so tested it by shorting
the connection to earth, and it works.

Well, the lamp does.
--
Jim K


----Android NewsGroup Reader----
http://usenet.sinaapp.com/

BMC A Series oil warning light
 

In article ,
Graeme wrote:
On to the next little problem - oil pressure warning light always on. I
fitted a new pressure switch a while ago, which made no difference so
checked today, and found that the light is on (with ignition) even when
the wire to the sender is disconnected. Inspected the loom, with no
obvious damage, which suggests a short to earth somewhere in the rat's
nest behind the speedo. Bugger.

You're very trusting driving the car with the oil pressure light on. Not
something I'd do - unless it also has an oil pressure gauge showing things
are OK.

--
*Never underestimate the power of stupid people in large groups.

Dave Plowman London SW
To e-mail, change noise into sound.

BMC A Series oil warning light
 

On 15/04/2018 12:37, Graeme wrote:

On to the next little problem - oil pressure warning light always on.Â* I
fitted a new pressure switch a while ago, which made no difference so
checked today, and found that the light is on (with ignition) even when
the wire to the sender is disconnected.Â* Inspected the loom, with no
obvious damage, which suggests a short to earth somewhere in the rat's
nest behind the speedo.Â* Bugger.

Being a late (68) model, there are two yellow oil warning lights, one
for low pressure and the other showing clogged filter.Â* I have never
seen the clogged filter one lit in 22 years, so tested it by shorting
the connection to earth, and it works.

Oh well, out with the speedo.

Does it have a modern spin-on filter (which will have a clogged bypass
valve) or the original canister variety?

BMC A Series oil warning light
 

In message , "Dave Plowman (News)"
writes
In article ,
Graeme wrote:
On to the next little problem - oil pressure warning light always on. I
fitted a new pressure switch a while ago, which made no difference so
checked today, and found that the light is on (with ignition) even when
the wire to the sender is disconnected.

You're very trusting driving the car with the oil pressure light on. Not
something I'd do - unless it also has an oil pressure gauge showing things
are OK.

Trusting, up to a point. Having removed the wire from the pressure
sender, and the light remaining on, I have proved that it is not the
pressure switch powering the warning light. I suppose it is possible
that the warning light would be on even with the wiring fault fixed.

(Thinking aloud) If I run a wire direct from the battery to a 12v bulb,
then to the pressure switch, the bulb will light. Then running the
engine *should* extinguish the bulb, which will prove the oil pressure
is OK. I think.
--
Graeme

BMC A Series oil warning light
 

Are we sure that this light is not operated by a relay of some kind, rather
than by the sensor directly?
Brian

--
From the Sofa of Brian Gaff Reply address is active
Remember, if you don't like where I post
or what I say, you don't have to
read my posts! :-)
"Graeme" wrote in message
...
In message , "Dave Plowman (News)"
writes
In article ,
Graeme wrote:
On to the next little problem - oil pressure warning light always on. I
fitted a new pressure switch a while ago, which made no difference so
checked today, and found that the light is on (with ignition) even when
the wire to the sender is disconnected.

You're very trusting driving the car with the oil pressure light on. Not
something I'd do - unless it also has an oil pressure gauge showing things
are OK.

Trusting, up to a point. Having removed the wire from the pressure
sender, and the light remaining on, I have proved that it is not the
pressure switch powering the warning light. I suppose it is possible that
the warning light would be on even with the wiring fault fixed.

(Thinking aloud) If I run a wire direct from the battery to a 12v bulb,
then to the pressure switch, the bulb will light. Then running the engine
*should* extinguish the bulb, which will prove the oil pressure is OK. I
think.
--
Graeme

BMC A Series oil warning light
 

In message , Graeme
writes

(Thinking aloud) If I run a wire direct from the battery to a 12v
bulb, then to the pressure switch, the bulb will light. Then running
the engine *should* extinguish the bulb, which will prove the oil
pressure is OK. I think.

Answering my own question, I have just tried a test lamp between the
battery and oil pressure switch. With the engine not running, the bulb
lights. Start the engine, and the bulb extinguishes, as expected (or
hoped!).

The fault must be a leak to earth, almost certainly behind the speedo,
which is a bit of a nightmare to access, due to the heater which is
directly below the speedo.
--
Graeme

BMC A Series oil warning light
 

In message , Brian-Gaff
writes
Are we sure that this light is not operated by a relay of some kind, rather
than by the sensor directly?

Brian, no, nothing so sophisticated. This is a 1968 Morris Traveller,
and the wiring for the oil pressure warning light runs from the ignition
to the bulb, then to the sensor for earth, with a fuse in circuit.
--
Graeme

BMC A Series oil warning light
 

On Sunday, 15 April 2018 12:56:29 UTC+1, JimK wrote:
Graeme Wrote in message:

On to the next little problem - oil pressure warning light always on. I
fitted a new pressure switch a while ago, which made no difference so
checked today, and found that the light is on (with ignition) even when
the wire to the sender is disconnected. Inspected the loom, with no
obvious damage, which suggests a short to earth somewhere in the rat's
nest behind the speedo. Bugger.

Being a late (68) model, there are two yellow oil warning lights, one
for low pressure and the other showing clogged filter. I have never
seen the clogged filter one lit in 22 years, so tested it by shorting
the connection to earth, and it works.

Well, the lamp does.
--
Jim K


----Android NewsGroup Reader----
http://usenet.sinaapp.com/

The oil pressure warning light is connected and"live" when the ignition is on.
The oil pressure switch just earths the other leg of the circuit. It opens when oil pressure rises.
So if you disconnect the wire to the oil pressure switch, the lamp must go out.
Unless the wiring is mis-wired or there is some strange fault.
You need to determine which side of the bulb is earth and replace that wire which runs between that (earth) side of the bulb and the oil pressure switch. & see what happens.
This wants looking at urgently.

BMC A Series oil warning light
 

In message ,
harry writes

You need to determine which side of the bulb is earth and replace that
wire which runs between that (earth) side of the bulb and the oil
pressure switch. & see what happens.

Harry, I am fairly confident I have eliminated a problem with the engine
itself. I have run a wire direct from the battery to a bulb, and from
the bulb to the oil pressure switch terminal. With the engine off, the
bulb lights, as expected, earthing through the switch. With the engine
running, the bulb extinguishes, indicating the oil pressure is
sufficient to operate the switch and therefore break the connection to
earth.
--
Graeme

BMC A Series oil warning light
 

In article ,
Graeme wrote:
In message , Graeme
writes

(Thinking aloud) If I run a wire direct from the battery to a 12v
bulb, then to the pressure switch, the bulb will light. Then running
the engine *should* extinguish the bulb, which will prove the oil
pressure is OK. I think.

Answering my own question, I have just tried a test lamp between the
battery and oil pressure switch. With the engine not running, the bulb
lights. Start the engine, and the bulb extinguishes, as expected (or
hoped!).

The fault must be a leak to earth, almost certainly behind the speedo,
which is a bit of a nightmare to access, due to the heater which is
directly below the speedo.

Unless you've had mice ;-) the most likely thing is it has frayed going
through the bulkhead, etc. But car electrics are odd things - have a habit
of defying logic.

--
*Don't byte off more than you can view *

Dave Plowman London SW
To e-mail, change noise into sound.

BMC A Series oil warning light
 

On Sunday, 15 April 2018 18:09:51 UTC+1, Graeme wrote:
In message ,
harry writes

You need to determine which side of the bulb is earth and replace that
wire which runs between that (earth) side of the bulb and the oil
pressure switch. & see what happens.

Harry, I am fairly confident I have eliminated a problem with the engine
itself. I have run a wire direct from the battery to a bulb, and from
the bulb to the oil pressure switch terminal. With the engine off, the
bulb lights, as expected, earthing through the switch. With the engine
running, the bulb extinguishes, indicating the oil pressure is
sufficient to operate the switch and therefore break the connection to
earth.

As others say I'd be wary of driving it with no functional oil warning light. But it sounds like you've worked out a usable bodge until it gets done properly.


NT

BMC A Series oil warning light
 

In message ,
writes

As others say I'd be wary of driving it with no functional oil warning
light. But it sounds like you've worked out a usable bodge until it
gets done properly.

I do take the point, and had another look this morning, pulling the
speedo out. Noticed the 'earth' wire from the bulb to the sender
changes colour somewhere, so must have been bodged at some time in the
dim and distant.

Long story short, I could not find a fault, so cut the existing wire at
the bulb end and ran a new wire from there direct to the oil pressure
warning switch. The light now comes on with the ignition, and goes out
with the engine running, as expected.
--
Graeme