Replaced solenoid valve. Repair summary: Turn off H/C water supply, disconnect hoses. Unscrew 3 screws rear of main panel. Slide front panel laterally then pull up to remove. Unscrew 2 screws on solenoid valve part. Disconnect spade electrical connectors and remove defective part. Insert new part and do everything I just said in reverse. It was so easy a drunken monkey could have done it.