Thank you all for the suggestions. My apologies it took a while to write back. I couldn't find a new battery where I was in Sweden for holiday, but now I'm back home in the Netherlands and have tried with a new battery. Alas there's no change.
I'm beginning to doubt my recollection of what is normal behaviour for the camera. When the meter is active mine only shows 0 (zero) in all modes (except M which seems normal).
If I half-press the exposure button the zero changes to two dashes - - which, as I recall it, is where the aperture value would normally be displayed, and change if the ring is turned.
I have checked in the manual about the AE lock, but it seems that it will be over-ridden when the shutter button is depressed. I don't find info that it would remain locked 'across modes' for instance. On my camera I can lock exposure in Ab mode and cancel the lock just as said in the manual. And in A mode I can temporarily lock exposure by half-pressing the exposure button.
What is possibly odd, however, is that every time I go into the A mode from Diff (but not from M) the L symbol is displayed immediately, as if the system is automatically locking exposure at whatever the camera is set to. Perhaps this is normal behaviour though.
I've tried all sorts of equipment combinations, with E12 and A12 mags, with the 80 Planar FE, the 40 Distagon CFE and the 350 Tele-Tessar FE, with the 2XE converter and the 2x Mutar, without anything mounted. There's no difference.
I don't exclude that I've missed some point in the manual even though I've looked in it many times now, so if something rings a bell do please let me know. I starting to think that there is something wrong with the electronic contacts because the camera behaves as if there is no lens attached. I guess I'll email Hasselblad Gothenburg and ask what they think.
Cheers and thank you for your assistance
Philip
I think you are on AE lock. see manual
Maybe...
View attachment 281534
This shows up in the Ab (Auto Bracket) mode. "0" is no exposure adjustment (1st shot) and L = locked. After the 1st exposure, the "0" will change to the next exposure adjustment that you set.
If replacing the battery doesn't work and you are in the USA you might try calling Hasselblad USA at 1-800-367-6434 ext 2 and ask for Dennis. He is the only certified 203FE technician in the USA. Unfortunately he only works part time. It's likely he can give you some idea of what to do. Regardless, once you've figured out what the problem is, please leave a post explaining the outcome.