General Aire 7604 16-20 Solenoid Valve Assembly 24V for SL16

I'm not sure how to rate this because I'm still not sure it's working correctly, two months after installing it. The instructions weren't extremely helpful -- giving help with the obvious things (unplug electrical connections) but not the details (what order and orientation the several sealing washers and o-rings go in). It was not exactly the same as the old one, so even being careful when taking the old one off won't necessarily help. The connection isn't leaking, but it seems very delicate, like it would pop off if something bumped it.There is water getting into the humidifier now, but the valve often emits a high-pitched whistle. I'd like to call the repair guy, but at the moment I can't afford another $50 part plus whatever the service call would cost.