Re: Diplomat ADP8332 error code F4
F4 means it’s not drained, or registered the fact that it’s drained in the allotted time. You can only check the obvious…clean the filter, then have a look in the sump area under the filter, there’s a black plastic grid at the 3 o’clock position. Make sure it’s clean…toothbrush and hot water etc but be careful not to poke anything sharp through the holes, there’s a rubber diaphragm behind it which could get punctured.
If that doesn’t sort it you may need an engineer to confirm a pcb fault 😕