1987 Spur - NAH 21836- Pressure Switches - Rolls-Royce and Bentley Forums
 
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post #1 of 6 (permalink) Old 12-02-2019, 07:04 PM Thread Starter
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1987 Spur - NAH 21836- Pressure Switches

My annunciator # 1 light is on and I think the brakes are bled properly. Does anyone know if I can remove the contact housing(see #3, Fig. G14-1, TSD G14-1) to this this switch to test, and how do I test it?

Larry B.
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post #2 of 6 (permalink) Old 12-02-2019, 07:18 PM
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The lamp should go off when the motor is running and pressure is built up to prevent the switch from grounding, causing the circuit to complete to ground.
You can get a false positive but it would be more important to find out if the lamp comes on due to low pressure in the system. The switches can be bled to elimate air at the switch piping.

LRL-41587C
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post #3 of 6 (permalink) Old 12-02-2019, 07:30 PM
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Given how easy and inexpensive it is to build a pressure gauge to test these systems, I suggest that any DIY mechanic do just that. That way you get a definitive answer, or as close as you're going to get to definitive.

Building a Hydraulic Pressure Test Gauge (B.Vogel)

You must only use the gauge on cars that use the same brake fluid. NEVER use a gauge that's been used on an HSMO car on a RR363 car or vice versa.

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The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


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post #4 of 6 (permalink) Old 12-03-2019, 09:36 AM
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Bleed the switches first.
If you still have a problem, remove switches and open them then replace diaphragm and check the main pin pushed by the diaphragm.
Pin should be replaced if old and smashed and stuck. Pin should be free and moving with diaphragm movement from pressure...

Esay to do

97 Continental R
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post #5 of 6 (permalink) Old 12-03-2019, 09:50 AM Thread Starter
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Thanks all.

How do I bleed the pressure switches, as the TSD is silent on this or I cannot read......
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post #6 of 6 (permalink) Old 12-03-2019, 05:05 PM
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On the SZ there is a ckassic bleeder, like on caliper, just be side the switches, I think on the SY too

97 Continental R
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