This is basic electronics. The voltage must reach maximum if the resistance goes to infinite. There is only virtually a current flowing...
Basic science requires that findings be adequately documented, especially when they are used to support extraordinary claims, such as the HAD. F&P failed to meet this fundamental requirement.
In the whole 1992 paper (1), the only explicit reference to the alleged phenomenon, that F&P will successively call "Heat After Death" (2), is contained in a couple of lines on the concluding page: "following the boiling to dryness and the open-circuiting of the cells, the cells nevertheless remain at high temperature for prolonged periods of time, Fig 8".
All they have provided for demonstrating this extraordinary behavior are two vertical lines drawn on Fig 8 and placed in the wrong position (3).
To support an extraordinary claim like the HAD, any normal scientist would have provided at least the detailed curves of the electric parameters (current and voltage) recorded during the last boil-off hours of Cell 2. On the contrary, F&P deliberately omitted to report these basic data, either in their 1992 paper (1) and in all the several subsequent documents, including the 1993 paper specifically devoted to the presentation of this alleged phenomenon (2).
In conclusion, there is no reason to believe that any HAD event occurred during the 1992 boil-off experiment.
(1) https://www.lenr-canr.org/acrobat/Fleischmancalorimetra.pdf