1970 Series II. The dash lever, wire and lever on my hot water valve all appear to move properly. The outside shaft on the plunger appears to move in and out properly. The problem is that the air inside never gets more than warm even with the fan on the high setting. I do have the flap in the air mix box set properly so all is shunted to the cabin but still only get warm air. Considering the water flowing through the valve and into the radiator in the box should be right below 200F I am not getting a high enough heat inside the cabin. Any ideas? Pictures show plunger shaft on valve in both extremes.

 

You might try back flushing the heater core. I had a similar problem on my Series 3 and found the heater core was partially clogged. A good backlash cleared it out and solved the problem.

 

I had the same issue, but the heater core was toast. New ones are available. Not a horrible job, just fiddly. Took the opportunity to clean and repaint the heater box.

https://www.sngbarratt.com/English(U...QM-GP69Vgsh5pN