Common Causes could include ambient air temperature is too high. Drive's cooling fans are no longer in operation.

Corrective action can include

Check the heat sink for dirt buildup. Check the cooling fans for dirt buildup.

Replacing the cooling fans if no longer operational. With no power applied the cooling fans should rotate freely by hand. Check the resistance of the fan coil using an ohmmeter. If it is 0 ohms, you can conclude the winding is shorted. If it is infinite, the winding is burned open. It should be somewhere between 300 to 500 ohms.

Reduce the ambient air temperature around the drive through external cooling.

If the internal recirc fan stops, the drive will fault on OH1 regardless of what temperature the heatsink is at. The internal recirc cooling fans are powered by 24vdc. You can measure the 24vdc power supply at terminals any of the S1-S8 terminals for a F7 drive to SN (note that SC and SP must be jumpered). The control board has a fuse on it that fuses the power supply. So this fuse can be checked.

On the larger drives, the two main fans that are probably 230VAC fans. These fans have a separate board called a Tap Change Board labeled 8PCB. On this board is a cooling fan fuse. Check this fuse as well. Using an ohmmeter the reading of a good fuse should be 0 ohms. When possible, remove the fuse prior to checking for a true reading.

CSH 01-14-09