Shuttle Valve advice

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Yes, I have replaced a shuttle valve switch plate in the past.
Before you replace the switch plate, you might want to check out the modification to the wiring, google "disco 2 svs mod" and you should get some ideas. The problem isn't always the switches, but the wiring inside the ABS modulator unit connecting the plate to the plug and socket on the outside of the modulator.
The switch plate can be replaced without removing the ABS modulator with care. You should find details of that too online.
There's also a load of information here on the forum, just do a search.
 
Find some nice PDF instruction on the modification. I think that I will first start with replacing the valve without removing the unit.
Safer in my hands!

Any more advice is very welcome!

Nic
 
First of all you dont replave the shuttle valve but a switch pack which in 99% of cases is good, fitting a new switch pack without the wiring mod might be useless, i quote myself from other forum:
The SVS issue was explained many ways but never this way, i edited the internal diagram of the ABS modulator concentrating on the SVS module(SWO500040), i marked where IMO the problems usually are with orange but in case of oil ingress to the switches those resistances(with red) will be affected and the fault is the same, with purple are the external wires of mod option B, blue is the switch pack(SWO500030), there are two important notes on the original scheme:
* TOTAL RESISTANCE INCLUDING CONTACT AND CRIMP RESISTANCE: R<0.017 OHMS for the connection which gives the main earth(that big earth connector below the multiplug
**TOTAL RESISTANCE INCLUDING CONTACT AND CRIMP RESISTANCE: R<0.04 OHMS on the refference earth(ground) circuit from SLABS to pin 8 of multiplug
SVSOPTIONB-3.jpg


so there will be SVS related fault code if the resistances of the switch pack are out of range(which from MY experience is rare) and if one or both of those two earth circuit resistances are out of that "tight" range(thats the most common IMO) corroborated with the modulator's internal circuit increased resistnce , so taking with external wires the switch pack in series between earth and the SLABS ECU's SVS input the internal circuit of the modulator is bypassed and the only case in which the 3 amigos will come on again is if the switches will be ruined by fluid ingress ... that's why i'm saying that the brake fluid ingress is not the most common issue cos many of those who made option B didnt replace the valve seals, some of them nor the switch pack just made the wiring mod and they haven't seen the 3 amigos generated by SVS fault code again...i hope it makes sense
 
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