The FH error code is caused by the following conditions: If after 30 seconds the control does not detect water entering machine, the valves will be turned off and the error code will be displayed. OR If the control has turned the water valves on and after 8 minutes the flow sensor has detected 10.5 gallons of water passing through it, but has not detected the pressure switch trip, the valves will be turned off and the error code will flash.
Your symptoms point toward a siphoning problem or a pressure switch failure.
Here are some troubleshooting steps that may help:
Check the drain hose to make sure that it is properly installed according to the installation instructions. Make sure that the drain hose is not stuck way down the stand pipe. Make sure that the top of the stand pipe is not taped shut so that it is air tight. A problem with proper drain hose installation could cause a siphoning problem and may result in this fault code.
If you are able to safely access internal components in your washer, follow these steps to check the pressure switch:
Unplug the washer to completely disconnect electrical power.
Remove the top panel of the washer. This panel is secured by screws at the very back of the washer. Remove the screws and pull the top panel back and up to remove it.
Locate the pressure switch. It is Key 23 in the image below.
Make sure that the wire harness connections to this switch are secure.
Make sure that the pressure switch hose (Key 24) is properly connected to the pressure switch. If this hose is disconnected or damaged (kinked, pinched or torn), then it could be causing your problem.
If the wiring connections and the pressure hose appear to be okay, then you could have a stuck contact in the pressure switch. You may try tapping on the body of the pressure switch with the handle of a screw driver. Sometimes this will free up a stuck contact and allow the pressure switch to begin operating properly. If not, then the pressure switch will likely need to be replaced to correct this washer problem.
If you are not completely confident in your ability to safely access and diagnose this washer problem, I recommend calling a service technician to fix the washer.
If you need more help with this washer repair, resubmit your question with additional details including the full model number of your washer.