TM 10-3930-664-10 MALFUNCTION TEST OR INSPECTION CORRECTIVE ACTION Step 3. Engine speed too low. Increase engine speed with accelerator. Step 4. Check for leaks at directional control valve, hydraulic lines and fittings, or at mast cylinders. Report any leaks to Organizational Maintenance. NOTE The following procedures are used for Model MHE-271 only. 20. CAB HEATER DOES NOT OPERATE PROPERLY Step 1. Check to see if the heater fan switch is on in the low or high speed positions. Move heater fan switch to low  or  high  speed  positions.    If  fan  does  not  operate  on  both  speeds,  notify Organizational Maintenance. Step 2. Check heater shut-off valve to see if valve is in closed position. Move handle of heater shut-off valve to open position. 21. WINDSHIELD WIPERS DO NOT OPERATE Check for loose or broken wires at the toggle switch or at the windshield wiper motors. Report loose or broken wire connectors to Organizational Maintenance. 3-13