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Discussion Starter #1
Well, I have been driving the 1971 Corniche a lot lately (we still work from home in our Covid-environment, so I mainly go out for grocery runs to take groceries to my elderly mother!)

All is going well. There is one issue that keeps popping up, and has been the subject of attention over the years. The left brake fascia light sometimes lights up and stays on. The braking functionality is, however, not perceptibly affected. If one "tests" the lights and oil on idle, by pushing the "test" button on the dash, the little fellow goes out. At times it might come back. Testing the pressure in the system has suggested all is well.

Any ideas? By the way, the power steering tightness has worked its way out of the system - must have been an air-bubble.
 

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What brake lite is on? Level? or System1 or System2?
 

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Let's hope it's the "Level" light, which is the easiest to rectify as that's generally a sinking float, which can be repaired or replaced.
 

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Discussion Starter #4
It's the left "brake" light. I think that's supposed to be the lower level?
 

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On a SY car, there is no such thing as a "lower level". The reservoir is divided in half, each with a float that are wired so either side, when low on fluid will trigger a fluid level low lamp. After running the car, wait 4-5 min after off and notice the levels on the sight glass. IF, the level returns to a "normal" range, you're ok in regard to level.
When you are driving, System 1 or 2 may come on. If on when driving, you may have a troublesome brake pressure switch.
If you perform your own work, become familiar with the hydraulic system. It is not for the faint of heart. If not a DIY'r, I would suggest a RR tech familiar with the system. It may be time to replace hydraulic hoses if data can't support changing them within 20 yrs.
 

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Discussion Starter #6
On a SY car, there is no such thing as a "lower level". The reservoir is divided in half, each with a float that are wired so either side, when low on fluid will trigger a fluid level low lamp. After running the car, wait 4-5 min after off and notice the levels on the sight glass. IF, the level returns to a "normal" range, you're ok in regard to level.
When you are driving, System 1 or 2 may come on. If on when driving, you may have a troublesome brake pressure switch.
If you perform your own work, become familiar with the hydraulic system. It is not for the faint of heart. If not a DIY'r, I would suggest a RR tech familiar with the system. It may be time to replace hydraulic hoses if data can't support changing them within 20 yrs.
Thanks Wraith. As you may have gathered, very much not the mechanic here.
 

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As an aside, always remember, "A picture is worth a thousand words," and you can attach 'em, straight from your smartphone if that's how you've taken 'em.

If you know (or suspect) you can't describe it accurately, always feel free to include a photo of what it is you're trying to get information about.
 

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Discussion Starter #8
As an aside, always remember, "A picture is worth a thousand words," and you can attach 'em, straight from your smartphone if that's how you've taken 'em.

If you know (or suspect) you can't describe it accurately, always feel free to include a photo of what it is you're trying to get information about.
A salutary principle to bear in mind, no doubt, but in the instant case, the issue is simply the lighting up and staying on (until pressing the test switch) of the left fascia brake light. There are two brake lights on the fascia, and the one on the left lights up and stays on erratically. Not sure taking a photo of this would add much illumination or explicatory effect!
 

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Well, I'll have to disagree, as the Corniche cars were very often "experimental" in that features later to be introduced to the SY series more widely were adopted on them earlier to much earlier. Having photos of virtually anything, including the dash warning light layout can give a lot of information.

That being said, if you have had the system pressure checked, and it comes out fine, there's a decent possibility that the pressure switch has become stuck open. See section G6 of the workshop manual. These switches are normally open, and when they are the lights illuminate. When there is enough pressure behind the switch diaphragm it closes and the light goes out (kinda the reverse of what we'd usually think in regard to a switch turning something on/off). There are times when the contact that slides "gets sticky," and often disassembling the pressure switch, thoroughly cleaning it, lubricating the areas that are supposed to have RR363 with it, and putting it back together will fix issues for a long time. You can also buy a rebuild kit. I don't think there's much difference in the pressure switches over the years, and here's an exploded view:

28502


If the system is pressurizing correctly, and I'll presume it is, your pressure switch has likely "gotten sticky" and needs to be overhauled for the system where this is happening (system 1 or system 2).
 

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Discussion Starter #10
Excellent - that's very useful. And point taken re photos. Next time I bring it in mechanic was going to confirm pressure is okay, and then was going to check out the switch. So seems we are on the same page.

She's driving so nicely at the moment, by the way!
 
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