I have a problem with a Daewoo forklift BR15s appears the fault code F5, when you turn the machine enters and leaves the contactor which activates the hydraulic system and power steering only works, not forward or back.

Hello John,
I have 9 of these machines and they can be very troublesome to diagnose. I dont have my manual with me now, but can send you the Daewoo manual in PDF form during the week. The faults usually are the Logic itself, or the main drive amps. One thing that ruins the power amp and logic is the batteries go too low in voltage. Factory spec is 45 volts! i raised the cut out to 47...as high as it goes. Since Daewoo does not have the lift cut out when the battery is low, the drivers tend to keep going even when the alarm goes off...dragging the battery down and raising the amps. Also, none of my trucks had fans, causing more failures. It's not uncommon to blow the logic and a power amp. from a low or shorted battery. also, the steer pot must be centered or the truck will send too much current to the inside drive motor on tight turns. You need the flashware to adjust this!
To diagnose a bad power amp, swap the left and right with each other and see if F6 appears.
I'll re-check my codes on Monday. If you would like the service manual, i can email it to you.