Potterton Puma 80 high pressure

I have Potterton Puma 80 installed in my house and it was working fine for more than one year or so. Recently, my circuit breaker went off and after switching it back I am seeing red light against "Low system Pressure". Pressure gauge has two needles, one is Red(bigger size) and other one is black (smaller size). Both of these needles were on 3 bar. I tried to drain the radiator and managed to get the black needle back on 1 bar.However Red needle is still on 3 bar and system in showing red light against "Low system Pressure". I have tried searching the web but could not find a way to depressuarize the system.Any pointer on what to do in this situation will be highly appreciated.

The red needle is a marker that you can physically move with your fingers,used as a refferance point for the black needle.The low pressure light is possibly a low pressure switch fault,i.e it may need removing and cleaning/replacing.While your down there check for any water leaks around the D.H.W diff/switch as if this has a tendancy to trip electrics if if leaks,also check the rear of the mod board [p.c.b] for any burning.Lots of threads on this boiler.

Thanks for your reply.

pcb looks fine. THere is no indication of burning. Also I don't see any dripping.

I tried to drain all the water by opening drain switch on radiator, but it is taking too long. I have been waiting for more than 15 mins and still water is trickling from radiator. pressure gauge is now indicating around 1 bar.

I am trying to find DHW switch but dont appear to find it. What should it look like? There is one blue device (may be a switch) with two lead (red and black) coming out. I am not sure whether it is DHW flow switch or not...