When performing any tests or repairs on forklift electrical systems, always disconnect battery and discharge the capacitors.
The below photo shows a few different styles of battery connectors and how to disconnect them from a forklift.
After disconnecting the battery connector, a simple method is to discharge the capacitor is to press and hold the horn button until capacitor is discharged.
NOTE: This method does not work on all forklifts. A better method is to use a resistor or a VOM set to a high voltage scale.
A 220 ohm resistor will work well if placed across the capacitor leads. Keeping fingers away from leads hold it for a couple of seconds to insure it is fully discharged. To make sure the capacitor is discharged, measure the voltage with your VOM. You can also use your VOM to discharge the capacitors. This works very slowly due to the high internal resistance, this is slow but very safe you will be sure the capacitor is fully discharged when the meter reads zero volts. Don't forget to disconnect the battery first!
Never replace fuses with other than the proper value fuse. If a fuse continues to blow that means there is a short or partially shorted circuit in the system.