Hey Steve,
I suspect the spring inside the AFM may be damaged or hanging up due to rust or some other de-generative (electrical) crap.
The rubber plug atop the AFM can be (carefully) cut loose from the body to check for these obvious problems.
Hint: Trace the E-2 terminal inside as this is the low speed setting, then vb, then vc
(I would suggest waterproof "goop" to re-fasten the lid.)
If you see nothing "poopy" in there you'll need to go to the attached resistance measurement and inspection criteria.(see attached photos)
I will assume if your a profesional you've already checked the manual movement of the measuring/compensation plate?
How's your Sarasota weather bro? (We got 8 inches of rain in Ft Laud)
Tim
mr2tim
Please let us know how this works out as some Club members may use this information in the future on their cars!