Western plow will not go left

Try bleeding the cylinder also could have dirt when you changed only takes a small amount of dirt to jam the control valve

check for air in cylinder may have to bleed the line and cylinder

Hydraulic fluid doesn't really freeze. When it does, we wouldn't be around to see it. You need to go threw electrical. Go to there web site and see if you can get a diagram for it. Old systems are fairly easy to go threw. Newer ones have PC boards. Older ones, the stick/switches go bad first. But it always wise to loosen, then tighten the nuts that hold wires first. Corrosion sets in because it isn't used for so long.

Take it back.

It is electric over hydraulic most are, make sure the solenoid is clicking when you try to turn the plow. One side is working see what one is clicking the other one would be the culprit. If the solenoid are working then the problem is internal to the valve body. Make sure you haven't bent the rams that will cause this as well. If you have you will hear the hydraulics trying to over come this. Make sure the power is getting to the solenoid as well to make them click. Sometimes the switch inside the cab will break inside and not send the electric signal to the solenoid. inside when they do this they are moving a spool valve to redirect hydraulic flow of fluid to one ram or the other. Hope this helps :-)

check the wiring connections on the plow solenoids to be sure they are correct, the second step is check the controller box, using a continuity check via multimeter set for DC voltage. I have an old western plow that had similar symptoms, and was the controller box.

Needs bleeding,got air in the line.

bleed the ram for that as well

did you try cleaning the solenoids for the plow? i think this would solve your problem