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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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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 |
#2
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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/ |
#3
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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. |
#4
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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? |
#5
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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 |
#6
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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 |
#7
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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 |
#8
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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 |
#9
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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. |
#10
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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 |
#11
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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. |
#12
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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 |
#13
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BMC A Series oil warning light
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