thwaites 4 tonne year 2000 forward & reverse spool valve

[smarttee]

Hi Everyone , can anyone tell me how the spool valve works, there appears to be two solenoids operated by the switch on dashboard for forward and reverse. At the moment I can only move the machine forward . I have power at solenoid when F or R selected, solenoid coil value similar.
Photo attached of VICKERS spool valve.

thank you

IMG_20200905_155235.jpg

IMG_20200905_102213.jpg

[kaos]

I'm not familiar with your machine, but I would expect one coil to be energized for forward, and the other for reverse. From the photos it appears that the connectors are the same, so one experiment would be to swap them. This should make the selector lever work "backwards". If the machine then starts moving in reverse only (with the selector in forward), it's probably an electric issue. If the machine still moves only forward (with the selector in reverse) it's more likely to be hydraulic or mechanical.

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Regards, Kári.

[cobbadog]

Try cleaning up ALL the electrical connections and try what has been suggested by kaos, that is a simple and safe test. If you get the result from swapping over the terminals then you need to look at the linkage that must move to make the solenoids switch on and off. So check there is free and easy movement at the solenoids or that the Vickers switch is not seized. I too have not seen this set up as it is way to new for my old toys but it should be a simple thing to track down but if the Vickers switch is faulty and cannot not be repaired I dont know the cost of a new one but at least it will be available.

[essexpete]

I guess if you get the similar reading at the solenoids when switched the that rules out the fwd/rev switch and circuit. The JCB fitters swap over the solenoids as suggested above to eliminate solenoid fault. Did the fault suddenly develop?

[cobbadog]

The other thing to consider is that the solenoid could be stuck and not moving. This will give you the correct coil readings but if it is not moving you wont have forward n reverse.