International Plow Truck, front plow hoist won't lower.

[Kurt Montandon]

The hydraulic ram on the front of the plow truck (a 2020 International HV) won't lower - and it's the only hydraulic on the entire valve assembly that isn't working.

It's not a problem with the electronic controls, as I've put a wrench on the manual control, and the "Raise" part of the double-action valve works (it's hydraulic raise, gravity lower). It's raised all the way, but I can hear it working and the pressure jumps on the gauge.

Any suggestions to this non-mechanic?

Here's a picture of the hydraulics on the hoist, and the valve assembly, with the raise/lower for the front plow highlighted:

 

[crane operator]

Swap hoses with a different function and see if it's the cylinder or the valve.

 

[westerner]

I have found a few quick connects that suddenly went stupid...