Hotpoint FFA74 – fault-find assistance required

Hi all,

I’ve got a Hotpoint FFA74 that isn’t well. I’ve read the background information on this site (which was very interesting), but I’m looking for a bit of assistance in how to diagnose a fault step by step.

The situation is this,

The freezer temperature warning light is on.
The fridge is cooling fine.
If you hit the ‘fast freeze button’, the warning light will eventually go out, but when you turn it off the freezer compartment heats up again and the warning light comes back on.
The freezer is cold, the fridge is fine, so I don’t think it needs re-gassing.
I can hear the compressor running, and it still cools, so I guess thats ok.
I’ve taken the baffle off the inside rear of the freezer compartment and the fan is not restricted in any way.
There was a small amount of ice build up on the evaporator, I have defrosted this, and powered the freezer back up.
The freezer has cooled down again, a fine layer of ‘frost’ built up on the evaporator (presuably not yet enough to trigger a defrost cycle).
I can see the fan working to circulate the cooled air around the freezer compartment.
The warning light is still on, but the compartment seems cold.

So assuming the simple action of drefrosting the freezer doesn’t work, what should I be testing next?

Thanks in advance.