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Discussion Starter · #1 ·
I wonderer if someone could advise me please regarding a low fluid warning I keep getting on SRH14914 1973 Shadow. Sometimes I start her up and I get 'Low Fluid' and 'Partial Brake Failure' lights on. I don't think it's the reed switches in the reservoir as I've tested them with a multimeter, and even with the wires disconnected the warning lights still are on. What else could cause this please? Other times the light does not come on, and the reservoir level is perfect always. Thanks, Dylan
 

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level and pressure warnings are 2 very different things. The pressure lamp indicates your system is dangerous, ie very lo pressure. Run engine for 4-5 min. Shut off. Turn key to on. Press brake pedal to the floor, let it return and repeat until both lamps come on System 1 and System 2. They will come on at different times and remember how many pumps it took to illuminate them. This is basically a stress test to test the overall safety of your system. Your system most likely needs new accumulators.
Have you flushed the system in the last 2-3 yrs?
 

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Discussion Starter · #3 ·
Hi, thanks for your reply. Yes the system is all new. SRH14914 had been off the road for 34 years when I bought her in January this year. We've replaced the brake pumps, both accumulators, all 6 calipers and all the hoses. I've had pressure lights before when there was air locks but all working fine now. It's a fluid level light that's causing problems now but I'm fairly sure there's nothing actually wrong with the level. I'm wondering it the wire to the reed switches is damaged and earthing somewhere, or maybe there's a faulty solenoid somewhere? Regards, Dylan
 

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Use a mirror to inspect the 2 terminals underneath and trace it to the cable that routes to the tank. Sometimes there is a resistor on a phenolic board and things can go awry there as well. Try bleeding your 2 pressure switches again within the engine bay, they can be stubborn and sometimes a whack makes it behave. They are an easy rebuild.
 

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I'm wondering it the wire to the reed switches is damaged and earthing somewhere, or maybe there's a faulty solenoid somewhere?
Hi Dylan

I think you are right on the money here. You could try disconnecting the wires leading to the reed switches and measuring the voltage. You should get 12v (10ish in practice). If there is 0 volts it will show there is a short in the wire. I am pretty sure there are no relays/solenoids involved in this circuit.

If you remove the central walnut panel you will be able to unscrew the light warning unit and pull it forward slightly to see the wiring connections. You could then check for continuity to earth.

Just a couple of suggestions.
 

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Discussion Starter · #6 ·
Thank you - I've looked at the connectors to the reed switches and there is just one wire with two connectors (one for each switch) and the wire just goes into the loom into the bulk head. This morning the warnings are off again, so I'll have to wait for them to relight before I do further testing. Many thanks - I hate intermittent faults!
 

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Have you examined what's going on with the floats in the reservoir?

The ways things can go wrong with those are myriad, but if you've got something going on where a float keeps moving to each side of "the light illumination limits" that could be it right there.
 

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Discussion Starter · #9 ·
Well I thought I had ruled out the floats as I have tried pushing them down to the bottom and I can hear them clicking, so I assumed they were working correctly. Also with the wire connectors removed the light remains lit. Regards, Dylan
 

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Soon after I bought my car many years ago, while tracing assorted electrical gremlins I found a corroded pin on a toe-board connector on the engine side.. I removed all the connectors, brushed the pins with a stainless steel wire brush, slathered the lot in generous dollops of Vaseline and replugged. On the way I discovered one completely corroded through pin - fortunately there was a spare position on the connection. This solved a few of the weird bugs, and the electrics have been reliable ever since. ALL cars of this age have electrical corrosion problems if they have been driven and not stored in A/C storage.

Beware - some pins are permanent 12volts.

I made a bent wire thingy to help with the connector removal - they are "difficult". Same thing goes for Spirits but the "bent wire thingy" has to be subtly different.

Alan D.
 

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Discussion Starter · #11 ·
Hi, Unfortunately this Low fluid level issue has started again. I'm trying to find the lamp and reed switches on the wiring diagram but can't see them anywhere. I'm looking on Sheet 2 for RHD cars from chassis number 9000 and have been looking for ages. Does anyone know where I can see them please? I thought the lamp at least should be in this area below. Thanks.

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Discussion Starter · #13 ·
Thats brilliant - thank you. I was looking all over for that. I need to work out what is going on here - as far as I understand it the reed switches provide an earth for the warning lamp when the magnet triggers it. My switches are working fine, and when I remove the wires to them the lamp remains lit. So somewhere the wire is shorting to ground. Do you happen to now what the '8' refers to on the diagram please? Is that a connector somewhere maybe? Thanks again. Dylan

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Check the diodes between the warning lamp and the warning lamp test relay. If one is faulty it can connect a ground to the warning lamp bulb. It could also be a faulty warning lamp test relay with an intermittent short.
 

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Discussion Starter · #15 ·
Great idea thanks. Do you know if the diodes are behind the dash near the lamps please?
 

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I second Jim's opinion, had similar issues way back on my 72 Shadow and I traced it to a 25 cent diode.You may have to do a component location dig within the manual, but you will find it. You're on the right path.
 
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