Black Water Valve with a wire pull opener, problem

I had a problem where my black tank valve would not close and leaked down to the end of the drain line. Very messy to remove the cap. I installed an external cut off valve for a while which was OK, but it froze in cold weather. Finally, I installed an electric valve. It's expensive but works great and never a problem.

After a year of working the situation I put in the shop and had them repair the problem. Thank goodness I did. They charged 3 hrs but they worked on it all day. I watched them all day. Had to replace the valve and cable. A nasty job.

There is a valve lubricant available that can be poured into an empty tank. It is available at most RV dealers as well as CW. I have used this with success. Like you, my valves are all concealed so this was the easiest.

Eyeland:
I had the very same problem you have and it got so bad that I once pulled the seals loose trying to open the valve to the gray water tank. I now know what I did to cause the problem. One thing I did wrong was to put bleach in the tanks to get rid of odors. This causes the seals to degrade. The other thing I did wrong was to use WD40, vaseline and plumbers grease at separate times in a effort to free up the slide. Wrong thing to do! All of the above lubricants are petroleum based and will cause the seals to swell up and make it very difficult to move the blades. I even replaced the entire valve assemblies twice with the same results.
I've since bought new valves again and relocated them so that they are accessible whereas before, they were tucked under and in the middle of the vehicle. I now know to use silicone grease (a non petroleum product) on the blade portion of the valves and have not had a problem since. This stuff is a little harder to find and pricier than plumbers grease but I know HD has it and it can be found online.

If memory serves correctly, that cable will detach from the valve body fairly easily, probably 2 bolts on the valve body. Disconnect the cable, then use needle nose pliers to push/pull the valve blade. If the valve operates freely, then the problem is on the cable end.

You can try lubing the cable, maybe not torque the bolts so tight when reattaching.

do this in a place where you have a water hose handy, you could have a real problem ,, and use the sprays they work, pair goggles might help .

Have you seen this video??
I did this but used silicone spray lube (not WD-40) and my valves now slide as smooth as silk.
Cheers,
-Mark

You have to hold your nose and have a bucket there and open the valve. Spray the heck out of it all with silicone spray and work the valve open and closed a lot till you are happy. If not happy, replace the valve.

We had a the black valve handle come right out one time like that, where the other end had parted somewhere inside under (above) the underbelly. Lucky for us, it was a warranty item. The dealer techs did not enjoy that job. That was years ago, and I am waiting for it to happen again so it will be my turn to fix it. :(

I have another knife valve I put in at the sani-dump end and it responds to silicone spray like magic. Same with the cap for getting it on and off easily.

The vale is very difficult to open and to close. I am concerned that the wire or valve will break.

I'm not sure if you've stated what your problem is or if you have, I missed it. You said you have a black water valve with a wire pull and a problem. Exactly what is your problem? Does the valve not pull open, is it hard to pull, does the valve not close, does the valve leak or does nothing at all happen? You're going to have to step up to the plate here and tell us what your problem is before we can reply with a solution to your problem.